Which lock do you have on your door ? Most people wont know what type of lock they have so heres a guide:
Rim Cylinder – often called a Yale lock
Euro Cylinder – Mainly seen on upvc or composite doors
Sash Mortice – sometimes referred to as a Chubb lock
Moritce Lock – Like the sash mortice both have a british standard kite mark with 5 levers, anti-drill, and anti-pick curtain.