Done fair amount of searching but not come across anybody asking similar question previously. Currently have a knackered window/sidelight in a timber frame beside a timber front door (in a timber frame, obviously). I need to replace the sidelight but was thinking of doing it in uPVC. I would need to make sure that the profile of the window isn't deeper than the door and cut out the timber frame of the window. Is this madness or is it a regularly done thing?? I want to fit uPVC because it's a quicker and cheaper option than getting a replacement timber window. Place is a tenanted flat. Appreciate any help.