Managed to get two of the screws undone. Turns out they're actually E10 torx. The garage can fight the other two as they have a bracket stuck over them making it almost impossible to get a decent purchase on them so rather than round them off I have soaked them in oil and let them be.
Also started to investigate why the rear windows don't work. Some basic poking got the motors out and established that the motor physically turns freely and its gearbox moves without issue, as do the regulators... I did wonder if the windows had stuck in the frames, but the regulators move without issue if you manually move the windows, so frames lubed with PTFE spray.
Electrically, the switches work but there's something amiss in the door ECUs as there is a short between the two power feeds to the motor regardless of switch position which suggests a fault within the door ECUs as they contain relays that supply the motor rather than a software issue.