Repair of window Regulators
If your window regulator problem is the usual stripped drive problem, you can fit the regulator drive head from any contemporary BMC saloon as they all used the same basic unit with different arms for the different doors.
If you can get a REAR door unit, chances are that it won’t have had mush use in its life other than kids trying to wear it out. They are handed, so get the correct side! Also, ensure you get the correct drive, either ~3/8″ square drive or ~1” large hex drive.
All that needs to be done to fit it is to drill off the old saloon car arms and weld your ones on in their place, (after checking orientation, alignment etc).