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2026 Decision Guide

How to Choose a Door Lock in the UK

A 7-step method from a working South London locksmith — match the right lock to your door, your insurer and your budget without overpaying for features you won't use.

Locksmith South London 11 min read Updated April 2026 Rated 5.0 on Google
Short Answer

The one-minute version of this guide

Door material first: timber = BS3621 mortice, uPVC / composite = TS007 3-star euro cylinder. Never mix these up.
Read your insurance: most UK policies require BS3621 or equivalent on final exit doors — missing this voids claims.
Budget realistically: £180–£280 per lock fitted by a certified UK locksmith in 2026. Below £150 is usually unrated.
Buy the rating, not the brand: Kitemark + TS007 3-star or Sold Secure Diamond is what insurers check, not the logo.
Keyed-alike on moving day: one key across front, back and side doors saves a lifetime of hassle — ask your fitter to do it.
Smart lock? Layer it. Fit a certified cylinder first, then bolt the smart module on — never the other way round.
In This Guide

The 12-chapter decision framework

Built from two decades of South London call-outs and cross-referenced with current UK insurance wording, ABI data, and Sold Secure test results.

01Why lock choice matters financially 02The 7-step locksmith method 03Step 1: identify your door type 04Step 2: understand UK standards 05Step 3: match the grade to your risk 06Step 4: measure before you buy 07Step 5: choose the right keyway 08Step 6: decide on smart features 09Step 7: set your budget tier 10UK brand shortlist 118 mistakes to avoid 12Frequently asked questions
Chapter 01 — Why It Matters

A door lock is a three-way decision: security, insurance, daily convenience

Most UK homeowners buy a lock on price. That's the wrong first question. UK insurers offer 5–15% lower premiums for BS3621-rated locks on final exit doors, and in high-risk postcodes they make it mandatory. The lock pays for itself on the renewal alone.

Then comes security. Lock snapping — the hammer-and-grips method used in the majority of UK uPVC break-ins — takes around 15 seconds on a 1-star cylinder and zero seconds on an unrated one. A certified cylinder stops it. That's the gap between "insured and safe" and "claim refused".

And then there's convenience: how many keys, which doors they operate, whether you want a phone to unlock the house, who has access when you're away. That's where budget priorities start to matter. The working rule across our South London service area is simple — pay once to get it right, then enjoy a decade of not thinking about it.

“The locks that survive real UK break-ins haven't changed dramatically in ten years. The mistakes homeowners make when buying them haven't either.”— Locksmith South London engineer, fitting notes

This guide walks through the 7-step method we use on every advice call. It pulls from current UK insurance wording (ABI 2025), independent Sold Secure test results, and the brand patterns we see every week on the van. The deeper dives on each lock type live in our Lock Types hub and Locksmith Advice blog — and if you want a human to tell you what to fit, send us a photo. We've been the company Locksmith South London since 2015.

Chapter 02 — The Method

The 7-step locksmith method, at a glance

We use the same seven steps on every advice call, whether it's a Victorian terrace in Camberwell or a new-build in Croydon. Each step eliminates the wrong options so only the right lock stays on the shortlist.

Step 01

Identify your door

Timber, uPVC, composite, aluminium. Door material dictates everything downstream.

Step 02

Read insurance policy

Find the security clause. BS3621 wording is almost always in there. Miss this and a claim can fail.

Step 03

Pick the standard

BS3621 for timber, TS007 3-star or Sold Secure Diamond for uPVC and composite. Write it down.

Step 04

Measure precisely

Cylinder length, backset, door thickness, case width. Wrong size = wrong lock, every time.

Step 05

Choose the keyway

Patented / restricted stops keys being copied at Timpson without your permission. Worth the upgrade.

Step 06

Smart or mechanical?

Only smart-layer over a certified mechanical core. Pure electronic lock = insurance void, usually.

Step 07

Set the budget

Good / Better / Best tiers from £180 to £300+ fitted. Higher tier = longer key life, not just more security.

Bonus

Keyed-alike setup

One key across front, back and side doors. Tell your fitter on the first visit.

The next chapters walk through each step in detail. Skim if you already know the basics, slow down on the steps that sound unfamiliar.

Chapter 03 — Step 1: Your Door

Start with the door, never with the lock

The most common mistake we see on call-outs: someone bought a "secure" lock from Amazon without checking it fits their door. These are the four common UK door types and the lock mechanism each one needs.

Solid timber

Victorian, Edwardian, heritage oak

FitBS3621 5-lever mortice + optional nightlatch
  • Look for Kitemark stamp
  • Match to existing mortice pocket
  • 67mm backset standard

uPVC

Back, side & patio doors

FitTS007 3-star anti-snap euro cylinder
  • Measure cylinder length
  • Flush with handle plate
  • Never downgrade to 1-star

Composite

GRP skin front doors (post-2010)

FitTS007 3-star inside factory multi-point
  • Never replace the gearbox DIY
  • Ultion WXM is the trade default
  • Size matters — measure twice

Aluminium / Hybrid

Modern glazed, bi-fold, steel

FitSold Secure Diamond cylinder + reinforced keep
  • Check door thickness first
  • ABUS Bravus, Mul-T-Lock MT5+
  • Add security escutcheon
Choosing a UK door lock standard — BS3621 and TS007 Kitemark
The right standard beats the right brand — Kitemark first, logo second.
Chapter 04 — Step 2: Standards

The three UK standards worth remembering

The lock industry is full of stamps, stars and badges, but only three standards actually change an insurance decision or stop a real attack.

BS3621 — British Standard Thief-Resistant

  • Mortice deadlocks and certified nightlatches for timber doors.
  • Requires five levers minimum, hardened bolt and 10-minute manual attack resistance.
  • Look for BSI Kitemark stamped on the faceplate — not a sticker. Full detail on our BS3621 guide.

TS007 — Star-rated euro cylinders

  • 1-, 2- or 3-star rating split between cylinder and handle.
  • A 3-star cylinder stands alone. A 1-star cylinder needs a 2-star handle to match that tier.
  • Tests snap, drill, pick, bump — the four UK burglary methods. See our anti-snap guide.

Sold Secure — independent attack testing

  • Bronze / Silver / Gold / Diamond tiers. Diamond = specialist tools, highest tier.
  • Independent UK body (MLA-owned) — preferred by Secured by Design (police).
  • Diamond cylinder ~ TS007 3-star equivalent for insurers. Our standards explained page has the full cross-reference.
Chapter 05 — Step 3: Risk Match

Match the grade to your actual risk

Not every door needs the highest tier. Use this matrix to pick the sensible rating for the door in front of you.

Door / Use Risk Recommended Why
Timber front door on a terraced street High BS3621 5-lever mortice + BS3621 nightlatch Insurance default; defeats pick, saw & kick
uPVC back door onto a garden High TS007 3-star anti-snap cylinder (Ultion / ABS) Snap is the dominant attack vector on back doors
Composite front door — new build Medium TS007 3-star cylinder inside factory multi-point Housebuilder cylinder is often 1-star only
Aluminium patio / bi-fold Medium Sold Secure Diamond cylinder + reinforced keep Thin profile needs hardened body & security escutcheon
Flat-entry communal door Medium Rim nightlatch (BS3621) + mortice deadlock Shared responsibility; keyed-alike with building key
Internal bathroom / bedroom Low 3-lever sashlock or privacy latch Privacy, not security — no Kitemark needed
Garage side door Medium BS3621 mortice + hasp & Sold Secure padlock Burglars target garages for tool theft
Shed / outbuilding Low Sold Secure Silver closed-shackle padlock + hasp Deter opportunistic theft without over-spending
Chapter 06 — Step 4: Measure

Four measurements every UK lock buyer needs

The number one cause of returned locks on Amazon is the wrong size. Take these four readings with a tape measure before you buy anything.

Cylinder length (uPVC / composite)

Measure from the outside edge of the cylinder to the inside edge, through the door. Record as external/internal in mm, e.g. 40/50. Standard UK sizes are 80–110mm total.

Backset (mortice locks)

The distance from the door edge to the centre of the keyhole. UK standard is 57mm or 67mm. Wrong backset = new handle hole to drill.

Case width & height (mortice)

Open the door and measure the existing lock pocket. New mortice must fit within 2mm. Larger means routing wood; smaller means a rattle.

Door thickness

Used for cylinder length and strike plate depth. Most UK timber doors are 44mm; composites are 44–48mm; aluminium can be 55mm+.

The photo trick

Open the door and photograph the lock edge-on against a tape measure. Send the photo to us via Contact Us or WhatsApp — we'll confirm the exact size you need and the three best matching products, usually inside an hour.

Chapter 07 — Step 5: Keyway

Patented & restricted keys — the upgrade most people skip

A strong cylinder with a key that anyone can copy isn't really secure. The keyway defines who can duplicate keys and at what cost.

Open-profile keyway

Any UK high-street cobbler or Timpson can cut a copy in 60 seconds for around £5. Zero key control.

Avoid for front doors
Semi-restricted keyway

Specialty profile copied only by licensed dealers. Mid-tier control, reasonable cost.

OK for most homes
Patented / restricted keyway

Copies only at the factory with proof of ownership. Full key control — no Timpson cuts possible. Worth it on rentals and shared homes.

Best for key control
Coded key card

Provided with top-tier cylinders (Ultion, Avocet ABS). Proves ownership when ordering replacement keys and enables key tracking.

Keep the card safe
Chapter 08 — Step 6: Smart Features

Smart locks, honestly: when they earn their place

Smart locks sell on convenience. Our job is to flag when the convenience cancels out the security. These two lists decide it.

Fit a smart lock when

  • Underlying cylinder is already a TS007 3-star or Sold Secure Diamond
  • You run a short-let and need rotating guest codes
  • You have cleaners, carers or dog-walkers on time-limited access
  • You want auto-lock on close as a belt-and-braces habit
  • You value an audit trail of who unlocked when

Skip the smart lock when

  • Underlying lock is 1-star or unrated — electronics won't fix that
  • The product replaces a BS3621 mortice on an insured timber door
  • There's no physical key override for dead batteries
  • It's a cheap import with no Kitemark or SBD badge
  • Your insurer explicitly names BS3621 only

Our trade default: Ultion WXM 3-star cylinder + Nuki smart module. Mechanical key still works, certified cylinder passes the Kitemark test, electronics sit inside on a rechargeable battery pack. Full detail on Smart Door Locks.

Chapter 09 — Step 7: Budget

Good, Better, Best — UK budget tiers for 2026

Prices below are supply-and-fit by our engineers. Buying online and paying a locksmith to fit separately usually costs more — these are final all-in figures.

Good — insurer minimum

Entry Tier

from £135 fitted per lock

Meets policy wording, solid for low-risk doors and back-of-property entries.

  • Standard euro cylinder replacement
  • Basic 5-lever mortice (not BS3621)
  • Non-patented keyway, 2 keys

Best for garage side doors, secondary entry, rentals under refresh

Better — trade default

Protect Tier

from £200 fitted per lock

The sweet spot. Meets every UK insurer, resists all four attack methods, survives a decade of use.

  • TS007 3-star anti-snap cylinder
  • BS3621 Kitemark mortice with 5 levers
  • Patented keyway, 3 keys + code card

Best for 90% of UK homes — front and back doors, new builds, moving in

Best — premium

Fortify Tier

from £300 fitted per lock

Diamond-rated cylinders, high-risk postcodes, HMO / landlord-grade kit.

  • Sold Secure Diamond (Ultion WXM, ABS Quantum)
  • Master-key or keyed-alike system
  • Optional smart module on top

Best for high-value homes, HMO portfolios, insurance schedules with Diamond wording

Chapter 10 — Brand Shortlist

The UK lock brand shortlist actually worth buying

Hundreds of brands exist. These are the ones that consistently pass Kitemark testing, arrive on our van in bulk, and survive a decade on a UK front door.

Timber / Mortice

Union 2134E

The default British 5-lever mortice deadlock since the 1970s. Hardened steel case, solid bolt throw, Kitemarked in every size.

Why trust itFits the standard 67mm UK timber door pocket without modification
Timber / Mortice

Chubb 3G114

The premium step-up mortice. Anti-pick curtain, drill-resistant pins, and the key profile is harder to reproduce than Union.

Why trust itFitted to insurer-schedule homes across the UK for decades
Timber / Mortice

ERA Fortress

Mid-priced BS3621 with Sold Secure Silver on top of the Kitemark. Common on buy-to-let refurbs and letting agent specs.

Why trust itGood value without compromising on certifications
uPVC / Cylinder

Brisant Ultion WXM

The cylinder that redefined anti-snap. Hidden second lock triggers under attack; £1,000 guarantee sits behind it.

Why trust itDefault fit on composite doors in South London — Diamond-rated
uPVC / Cylinder

Avocet ABS Quantum

Sidebar sliders stop bumping and picking; molybdenum body stops drilling. Secured by Design approved.

Why trust itExcellent value 3-star + Sold Secure Diamond dual certification
uPVC / Cylinder

Yale Platinum 3-star

The best-known name with a genuinely certified body. 16 anti-pick pins, patented key section, smart-module ready.

Why trust itEasy replacement keys from Yale-licensed dealers UK-wide
Premium

Mul-T-Lock MT5+

Interactive key system, alpha pin technology, and a patent running into the 2030s. Fit only by authorised dealers.

Why trust itSerious key control — no Timpson can copy them
Premium

ABUS Bravus 4000

German engineering, Sold Secure Diamond, and an interactive pin system that resists electronic picking tools too.

Why trust itFavoured on aluminium and bi-fold doors across the UK
Smart / Hybrid

Ultion Nuki Smart

3-star Ultion cylinder core with a Nuki motor module inside. HomeKit, Matter, Alexa, Google Home compatible.

Why trust itOnly UK smart lock we fit without caveat
Chapter 11 — Mistakes

8 mistakes we see every week on UK call-outs

If you're buying a lock in 2026, don't do any of these. All eight have made our call-outs and claim refusals.

  • Buying by brand, not by ratingYale makes brilliant 3-star cylinders and terrible 1-star ones. Check the stars, not the logo.
  • Wrong cylinder sizeToo long = snap risk. Too short = can't operate the cam. Measure before you buy.
  • Fitting "deadbolt" hardware"Deadbolt" is US terminology. UK insurance requires a British deadlock — different mechanism.
  • Replacing a BS3621 mortice with a smart lockThe smart lock is rarely BS3621-certified. Insurance void on most policies.
  • Ignoring the multi-point gearboxA new 3-star cylinder in an old, worn gearbox stills fails. Service or replace both together.
  • Fitting the lock yourselfA 2mm pocket error turns a secure mortice into a rattle. Lock warranty is also usually void.
  • Not keeping the key cardLose a restricted key with no code card and you need the whole lock replaced.
  • Forgetting the back doorYour £250 front-door cylinder is useless if the back door still has a 1-star. Upgrade both.
Locksmith South London Expert Tips

Four tips we wish every new customer knew

Two decades of fitting locks across SW, SE, CR and BR postcodes. These four save customers real money every week.

  • Call your insurer before you call us

    A five-minute call to ask "what rating do you require on my final exit doors?" saves buying the wrong lock. Some policies demand BS3621 only, some accept TS007 3-star, some now accept Sold Secure Diamond. Write the answer down.

  • Budget the back door first

    Nine out of ten UK burglaries come through a back or side door, not the front. Spend your premium budget on the quieter entries where attackers have time — and fit the simpler certified lock on the front where a neighbour can see.

  • Buy one spec, key everything alike

    A single Ultion or ABS model across front, back and side doors, all cut to the same key, is the rental-mover's best move. One key on the ring, one spec on the schedule, one easy insurance answer.

  • Keep the code card somewhere boring

    The coded card that comes with Ultion and ABS cylinders is the single thing that lets you order replacement keys. Hide it in a folder labelled "boiler service" — not with the spare keys, never in a drawer a burglar would check.

Customer Reviews

South London homeowners, recent upgrades

Real feedback from customers who read a version of this guide before booking. Rated 5.0 on Google.

Read this guide the day my insurance renewal arrived — it flagged my uPVC cylinder as non-compliant. Called Locksmith South London, sent a photo, they identified an ABS Quantum 3-star as the right spec. Fitted next morning. Premium dropped £38 on the year.

PS
Priya S.Streatham, SW16 — ABS Quantum 3★

Just moved into a 1930s semi with four external doors and no idea what was on any of them. Ben walked the property, identified each lock, told me which two to replace and which two were already fine. Keyed-alike the new ones so now I carry one key for the whole house.

BN
Ben N.Forest Hill, SE23 — Keyed-alike fit

Wanted a smart lock for school-run convenience but didn't want to compromise on the mechanical security. Maria ran me through the Ultion Nuki option on the driveway — cylinder fit in under 45 minutes, Matter/HomeKit linked up perfectly. No regrets.

MC
Maria C.Dulwich, SE21 — Ultion Nuki smart lock
Chapter 12 — FAQ

Frequently asked questions

Answers to the questions our team gets on the phone every week from UK homeowners choosing a lock.

How do I know what type of door lock I need?

Start with the door material. Timber doors take mortice deadlocks graded by BS3621. uPVC and composite doors take euro cylinders graded by TS007 (1–3 stars) or Sold Secure (Bronze–Diamond). Aluminium doors take Sold Secure Diamond cylinders.

Never fit a mortice in uPVC or a cylinder in timber — match the mechanism to the door. Our types of door locks guide has the full walkthrough.

What security rating should my front door lock have?

For most UK homes: BS3621 on timber doors or TS007 3-star (or Sold Secure Diamond) on uPVC and composite. A 1-star cylinder paired with a 2-star handle reaches the same insurer-acceptable tier.

Anything rated below this is not suitable for a final exit door. See our insurance-approved locks guide for the full list of certifications that satisfy UK policies.

How much should I budget for a new door lock in the UK?

2026 supply-and-fit prices from a reputable UK locksmith are typically:

Entry tier: £135–£180 (standard cylinders, non-BS mortice). Protect tier: £180–£280 (TS007 3-star, BS3621 mortice). Fortify tier: £250–£350 (Sold Secure Diamond, patented keyways, keyed-alike).

Below £150 fitted usually means an unrated cylinder. Cheap now, expensive when the insurer refuses a claim.

Can I fit a door lock myself?

A euro cylinder swap is within reach of a confident DIYer if the correct size cylinder is sourced. A mortice deadlock is not — the pocket must be cut square within 2mm of tolerance.

DIY fitting of a mortice voids both the lock warranty (typically 10 years) and most insurance security clauses. Professional fitting is part of the spec, not an optional extra.

Do smart locks replace the need for a physical lock?

No. UK insurers still require a mechanical lock meeting BS3621 or TS007 3-star. A smart lock layered over a certified cylinder is the only configuration that satisfies both convenience and insurance requirements.

Our trade default is Ultion Nuki — a 3-star mechanical core with a Nuki electronic module on the inside.

Should front and back doors have the same type of lock?

They should meet the same security standard but the mechanism often differs. A timber front door gets BS3621 mortice; a uPVC back door gets TS007 3-star. Ask your fitter to key them alike so one physical key operates both doors.

Insurer-compliant and convenient. Tell the locksmith at the quote stage, not after fitting.

How often should I replace or upgrade my door locks?

Replace locks at every change of ownership, after a loss of keys, when the mechanism feels stiff or loose, and at least once every 10–15 years even on good locks.

Cylinders in uPVC doors age fastest because of the heavy duty cycle — budget for a 10-year cycle on those. Mortice deadlocks in stable timber can last decades if kept lubricated.

What's the difference between a lock and a cylinder?

A lock is the whole mechanism — the case, bolt, levers or multi-point strip. A cylinder is the replaceable core that the key turns, found inside euro-profile locks on uPVC and composite doors.

On uPVC and composite, 95% of lock upgrades are actually cylinder replacements — the multi-point mechanism is retained and only the cylinder changes. That's why cylinder specification is so important.

Keep reading

Related guides & lock pages

Every link below is a proper in-depth page on our site — not a filler stub.

Blog

Best Door Locks for Home Security UK

The ranked 2026 buyer's guide with our top 5 lock picks and their Kitemark ratings.

Read guide Standards

British Standard Locks Explained

BS3621, Kitemark, TS007 — how each grading system actually works, in plain English.

Read guide Blog

Types of Door Locks Explained

Mortice, cylinder, nightlatch, rim, smart — every UK door lock mechanism in one place.

Read guide

Explore the site

Home Locksmith Advice Blog Lock Types Hub Door Locks Hub Security Locks Hub Smart Locks Hub Areas We Cover About Us Contact Us

Related locks & mechanisms

Euro Cylinder Lock 5-Lever Mortice Lock BS3621 Locks Anti-Snap Locks Anti-Snap Cylinder Insurance Approved Locks uPVC Door Locks Composite Door Locks Wooden Door Locks Smart Door Locks uPVC Door Lock Repair

South London areas we cover

Croydon CR0 Sutton SM1 Wallington SM6 Purley CR8 Coulsdon CR5 Thornton Heath CR7 South Croydon CR2 Norbury SW16 Sanderstead CR2 Kenley CR8
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