Long story short, have had a small leak in the radiator for a bit or so now. car was losing a small bit of cooolant and had to top it up a little bit every few days. temperature is staying Normal. drove home tonight and its very cold outside, temperature was fine, then all of a sudden it was rising very fast, then it went off the scale. stopped for a few minutes and it went back down, drove for about 40secs and then it did the same, finally got home after 2 stops and checked the engine again. didnt seem too hot, radiator wasnt steaming etc, the only thing i noticed was a weird almost rattley noise, but the engine was the same as it always was, and it wasnt doing it all the time. Is the thermostat knakered? or the waterpump? Thanks guys