thanks for your response. It was suggested to have the rad fan on a switch, but i don't want the engine to overheat after being switched off. The fan only works on AC backup as it should do. I just want to make sure the wires exposed are the correct ones for the sensor.
ps - new thermostat has been fitted (my dad gave same diagnosis as you have!!)
thanks. If you can confirm those wires are correct, or if there's any way of testing to make sure, then I'd love the help.