Fitted a new lock today. Went down to Screwfix with the old one - "can I have one of these?" I naively asked. The one they sold me was the wrong size because it turns out the margins on these things are in millimetres. Anyway, got a replacement and after much sweating and the odd swearword, the job was done. Including breakfast, a quick google and 2 return trips to the industrial estate, took two and a half hours. Not proud of that.