If your UPVC/composite door key turns but won’t unlock there are several possible reasons.
Do you live on St Mary’s in Ross on Wye, or a new estate in Lydney? If your lock/key looks like this then your lock may be faulty. We replace plenty of these on these estates.
Because of the internal/external thickness of the doors, your options are limited for an alternative lock. Not many manufacturers make them in the length you need with the same level of security for your ATK lock replacement. These are British Standard 3* locks.
It’s only the front door locks with the thumbturn that are unreliable. The ATK ones fitted to your patio doors with keyhole both sides work ok.