I would just get the gasket replaced, the cooling system on the BIS is so fragile it isn't worth messing about. I would replace the thermostat, as this can be very problematical, clean the oil filter as they are a pain to do so often get ignored, get a nice clean (clear plastic) fuel filter ( and a spare one to be carried at all times) tween tank and pump as the tanks tend to be full of crap, also check the fuel lines, if you are not sure just replace them, we had a members car catch fire recently, it is an old car thing, not a 126 thing! and check the condition of the tyres, I had two original 1988 stomils on ours when we bought it, delamination does happen!! But once all of that is done, just make sure the coolant is checked and bled regularly and it should be fine.
Used to spend a lot of time in Wymondham, got family there.
Marc