Mike will probably come up with the part number but from http://r75.sytes.net/ "If your temperature display is showing -30deg. then there's a good chance there's a problem with the external temperature sensor. It's mounted on the inside of the front bumper low down on the driver's-side just to the inside of the headlight assembly. It has a plug/connector in the lead just back from the sensor. You should be able to access it from below by removing the under-belly panel from the engine bay. A quick check with a multimeter will show if it's open-circuit (a sure sign of a faulty sensor). Typically the symptoms of a faulty sensor are: display at -30deg. and system blowing hot on any setting except 'Lo'."
Didn't you say you were having Aircon problems as well recently?
the bumper has been off the car as ive had new fan motor fitted, when i collected the car the temp said -30 but after a few yard drive it went to -19 and stays there, the heater works fine on all settings.
thanks for the part numbers where did you find them? i searched the net for ages and couldnt find anything.
disconnected the battery and it has solved the problem outside temp now showing normal