If your window or door locks are stiff to use i.e. you have to lift the door handle up & keep it lifted just so the key will turn then it sounds like the door has dropped. This is very common and is down to the installer, try operating the lock while the door is in the open position, if the lock works smoothly & you don't need to keep the handle lifted then phone the installer/ window company and ask them to adjust it. You must lubricate all the moving parts on locks & hinges at least twice per year. Nearly ALL window companies & Installers will guarantee the LOCK, HANDLES & HINGES for 12 MONTHS ONLY.
We can service your doors/windows starting from £30.00. If you leave it too long, the lock could break leaving you locked out. A replacement door lock would cost you between £150.00 and £200,00.