Lost your keys? Find out whether you really need new locks.

Do lost keys actually mean someone can get in?

It depends on whether the keys could be traced to your door. A bunch dropped in a park with nothing identifying is low risk. Keys lost with a wallet, a tagged keyring, a letter, or anything showing your address are a real risk — and the simplest response is a cylinder change. If your keys were stolen rather than mislaid, treat it as the higher-risk case and change the locks the same day.

Re-key or replace?

For the modern UK euro-cylinder (the brass barrel in most UPVC and composite doors), it's almost always cheaper to swap the whole cylinder than to re-pin it. A British Standard anti-snap (TS007 3-star) cylinder is £35–£80 and fits in about 15 minutes. Traditional mortice locks can sometimes be re-keyed economically — a locksmith will tell you which case applies once they see the door.

What changing the locks should cost

For a typical home with a front and back door, expect £140–£220 for two anti-snap cylinders fitted with key sets. A single external door is usually £80–£130. Add a window-lock check for £50–£90 if you want it. Anyone quoting far above that should be itemising the difference.

Don't forget the other doors that key opened

If the lost key was part of a set that also opened the back door, side gate or garage, every cylinder that key fits needs changing — not just the front. A good locksmith will ask what the missing key opened before quoting, so the whole job is priced up front rather than door-by-door surprises.