Thought id post about my problem and fix, basically the temp guage on the dash stopped working, the car idled fine, fuel consumption didn't change, some folks said it was a dodgy risistor behind the dash, some said a knackered needle, I decided to say sod it and chuck in a new coolant temp sensor....after a false start with being supplied the wrong one (needed the oval plug not the square one) I fitted it and I now have a fully working temp guage, moral of the story...just because you don't have all the symptoms it dont mean its not the problem, check the obvious, think logically and understand what different sensors do and control, 
