New development:
I've since noticed that when the car is hard to start that there is excess pressure in the coolant hoses, which obviously there should be no pressure at all on a cold engine.
I loosened the cap on the expansion tank by a few turns and left it like that and I have since had NO hard start problems!!
Head gasket blown??? :(
Also, I have noticed the heating is not as hot at low rpm, even though the coolant gets to 104c, but if I rev the engine, the heat output from the blowers warms up and the coolant temp drops to around 80-90c
Head gasket blown caused by failing / blocked water pump perhaps?
There is no signs of oil in the water or water in the oil however. BUT I can smell exhaust fumes through the blowers when the car is stationary, and I think I can smell fumes from the expansion chamber too. There doesn't appear to be any loss in fluid either!!??