I'll get that exhaust sorted eventually.
After the success of the tailgate central locking - which has been working perfectly fine with no issues so far - I determined to investigate the inoperative passenger door solenoid. I strongly suspect I'm the first person to be in here since the door was sealed up with the moisture membrane since the solenoid I pulled out was made in West Germany, which hasn't existed for quite some time. Annoyingly, while the door seal on the same door isn't leaking anywhere near like it was, it is still leaking, so I'll be getting a fresh generic door seal to sort that out because I cannot be doing with water getting into my cars.

I hoped to open the case and find broken plastics or similar inside. Instead, I found that the case was almost impossible to open. I got there in the end with a model making saw, some screwdrivers, and a couple of trapped finger tips when the plastic snapped shut on them. Once inside, there was nothing obvious amiss, I'd managed to break a wire with a screwdriver, but I knew if that was the fault it could be repaired if needed. Nothing visually broken or missing inside once opened, and everything free moving as it should be, where it should be, so far as I could tell.


Now I know what the inside of the door solenoids look like and have a rudimentary understanding of how it all works. Further inspection revealed the little electric motor was jammed and, after a little patience to free it up, it was found to be dead. I expect it's worn out brushes inside and even though it's potentially repairable and I could put the case back together and refit it to the car, new replacement solenoids are very easy to acquire, and affordable. So I've ordered a replacement, which isn't identical but matches where it matters, and has been a successful replacement for other BXers with this problem.
I can't go further with that until the new part arrives, probably early next week, so since the passenger door card was off for this I decided to try out the experiment. The reason, I believe, that the inner weather strips are rolling when the window goes down is that a lot of the fuzzy flocking is missing, so the plain rubber is grabbing the glass. Now, you can no doubt get this weatherstripping new online somewhere but I'm a little concerned at how fragile the door cards are so don't want to be fighting the clips off to remove the existing strip, and I fancied giving this experiment a go just in case it does work and can be used on future projects. The following picture is fuzzier than the the thing I'm trying to illustrate.

After scouring shops - because I'm stubbornly trying to buy things in actual shops still - I secured some velvet ribbon of a suitable width and some hopefully suitable glue. If this was the exterior weather strip I wouldn't try this experiment because it's exposed to so much more sun and moisture, I hope being the interior strip it wouldn't receive quite as much punishment. The gecko on the packet is simply an added bonus and not the reason I went for this particular brand. It seemed more appropriate than a lot of the other offerings on the shelf.

Applied the glue to the weather strip, carefully align the ribbon, and then apply a bajillion tiny bulldog clips to keep everything as secure as possible while the glue sets. I did check to see if the velvet has a directional pile as it sometimes does, and this one seems to be on the length of the ribbon rather than the width, so it shouldn't bind up against the glass.

When I get the new solenoid fitted, I'll reinstall this panel and we'll see whether or not the experiment is successful. If it is, I'll do the driver's side too and we'll see how long it lasts.