Nick Gilbert, thank you! Been looking for the answer of how to replace the sensor all over the place!
The outside air temperature sensor costs £15 on ebay, or £54 from Renault. They charge about £30+ to fit it and it seems like a fairly easy DIY job!
For anyone else searching, the sensor is on the bottom of the passenger side wing mirror, looks like a black rain drop. This seems the case for most renaults, including my sport clio.
If the sensor is not connected for any reason the temp will not display and the climate control won't work at all. If the sensor is broken you will get high temp readings (around 40) and the climate control will not function correctly.
Phil
February 2013