As the others have said its probably the temp sensor, make sure you use a genuine one..
did you have a new Thermostat put in too? might be worth to check it isn't sticking
Hey man thanks for the advice, I have a new sensor on the way, I have my fingers crosses but this morning it was ok and when it was sitting bang in the middle the fan cut in and the needle went to red again with the stop sign, within 5 seconds it sat and stayed on zero.
I'll try the new sensor and see from there, I've done 5 lots of g12 on this fooker