Update:

I replaced the coolant temp sensor on the weekend even though when Gav did a full scan on my car and tested the gauges to make sure everything was working correctly it all came back clear. It's really strange, if I turn the car off then back on straight away it will reset to 0 but if I come back after say a half hour or so, it will show the correct temperature. Anyone have any ideas? Starting to think it mist be an electrical problem somewhere along the line?

Any help appreciated!