The engine had a lot of fuel in the sump - not good. The coolant looked pretty grim too. The time taken to diagnose and fix means it was easier to replace with a known good engine, and whilst off it looks like the piston rings may have had it. So a replacement one is in (video here), though straight away we had overheating. We replaced the (most probably original 26 year old) thermostat with a new one, and all was well.
It drives ok, especially as it's raised right up for conservative road settings, a bit more steering wobble than I remember but that could be the road wheels. It's going up Tuesday for a good check over suspension wise. It also needs good clean inside, it's pretty dusty... but it's had a Morrisons car wash at least!