Short drive, up to temp, no leaks visible at all no noises. The damp on the floor panel is on the passenger side but hasn't got any worse, no sign of any leaks.
Bottom and top rad hoses all look and feel fine.
Havnt checked for air locks in the water, although have run the engine with the rad cap off and the level is steady, liquid looks clear/good.
I wonder if the water pump could have failed for a short period then somehow started again. That might explain the brief period of very high temp followed by no symptoms. Seems a bit odd though to briefly fail....
The advice to use a torch was good. Ahem, I don't think this is connected to problem 1 but the torch reveals grease on the steering shaft, a fair bit of it and it's on the rubber boot on the drive axle behind it. Grease... where the heck has that come from? The steering rack perhaps? Looks a bit of a mess but no obvious impact on performance.
Sorry to add another challenge. By the way the mileage is 80k not 100k, I've owned it since new.
Thanks for all the good thoughts.
Richard