As with most D2s it seems, most of the screws in the electronics box in mine have seized at some point, and previous owners have just yanked the top cover off. There was only one screw left usable by the time I got it. It's 'only' £100 new for both pieces, but I'm getting bored of throwing money at this problem child so repair rather than replace. In the pics the electronics box is removed from the car (since I was also working on the heater valve) but there's no reason you couldn't do this in place.
The brass inserts are all still seized to the rusty screws and so stuck in the lid. Mole grips didn't help so I just drilled the heads off them all.
I've found some more black screws and washers on ebay - they are on the way.
To repair the box itself I found these little beasties (also on ebay):
They're called 'D nuts' and are intended for use in wood but I figured they would work just as well in plastic. The teeth on them are a particular shape to prevent them backing out, and given the torque required to put them in its unlikely you'd be able to apply more than that to an M5 screw so they'll be pretty solid.
You can see the difference to the original brass inserts here:
The new inserts are designed to fit a 7.5 - 7.9mm hole which, conveniently, is a little bigger than the one the old inserts leave when they pull out
Drill out to 7.5mm:
The new inserts have a flange on the top so the holes need countersinking slightly using a 12mm drill to allow them to sit flush. That's important to allow the lid to seal properly. Well, as best as it can anyway
The new inserts have a 5mm hex socket in the top to allow them to be screwed in:
one done:
and all complete:
Fixed for a fiver and an hour's work
New screws with anti-seize grease should mean this will outlast the car.