Hi, my name isXXXXX apologize for the wait. On your windows the problem is usually the switches or the window motors. You can spend about £300 per window if the motors are bad. Switches aren't nearly as expensive. I'd estimate about £50 per switch. The boot lock could run in the £175 range. For the rear axle whine I'd estimate about £500 for a good used rear axle.
I'd probably offer less for the car. If you can get it for under £600 I'd call it a good deal. Especially since you have the parts car. Let me know if you need anything else. Marty