The build

Hi Mikey.  Its a disabled access supposedly stable door, but it not what I really wanted. He built it in a door frame with a tilt and turn window at top, that was first to break.  Its in the kitchen extension, so seems to be set into a upvc surround, which has the locking system in. Its the lock and hinges that is really broken, as it seems to have dropped but there is no adjustment left. My husband can fit yale locks, so hoping he can fit the weird upvc lock.

UPVC locks are easy to change there are just a few screws that hold them in place. UPVC adjustment can be harder as it might depend on whether it was fitted square in the first place, if it was fitted by a handyman originally they have a habit of over screwing the frame fixings and pulling the plastic frame out of square, you are then fighting with the packers on the hinges to try and realign it. There’s generally 3-5mm tolerance in the hinges so not a lot of variation. Pop a spirit level around the frame and see if you can square the frame up first before messing with the hinges.
a local UPVC supplier is likely to have someone that can swap handles etc, if your husband isn’t confident then a call might fix it for few quid instead of having to take it out.