Oil change with the obligatory pint of old oil up the sleeve.
Snap! except it took me two days, because I also took the sump off - first time since ~1993. Cleaned out the sludge. Painted the sump external, and also the filter pot, hence left them to dry overnight. Considered looking at the "filter" on the oil pump too, but in the end came to the conclusion that the Haynes manual has incorrect text as it talks about "simply remove the central bolt", which makes no sense, and also to "remove and replace the filter element". I don't think either exists (drawings don't show them) and it is just a gauze "strainer"?. I syringed some petrol through the bottom of the gauze and it sprayed happily out the top, so I assume this means it is not too gunged up inside, so I left it at that.
Also re-channelled the passenger-side door top, although as I was doing it a whole load of the steel bottom of the door-top came away and left some jaggy edges, so some random aluminium sheet pop-rivetted on to hide the worst of it. It still seems to be stiff enough to the mounting stud, so it will do a couple more years, but it looks like these door-tops have nearly completed their lifespan at ~30 years.
Over the last couple of weeks, re-sealed the tailgate lower. My tailgate has clearly been left down at some stage, while the vehicle has been reversed heavily into something, and one of the the tailgate "hinge" struts is slightly bent, I discovered. I could not see how I could safely bend it back with normal tools, so I elected to leave it as "history", as the tailgate does shut perfectly as is. It did mean a lot of fettling of the sealing rubbers before the tailgate would shut again. However, even without the bend on the one side, the other side required a lot of fettling too, so I am not convinced the seals I got are really the right fit for an old S2. My new riveting tool works a treat, though. The 5/16" long semi-tubular rivets work really well on the vertical seals. On the lower one, I used slightly longer 3/8" long rivets, because my metalwork is not a perfect straight edge, so the longer rivet helps to get the rivet all the way through the metalwork and seal.