Hi Chris
If the tips from ULP and John don't work there may be a problem with the aircon. If you bought the car from a dealer and have warranty, get it checked out as it could be one of the sensors which has failed - see link http://www.a2oc.net/forum/showthread.php?t=4542&highlight=climate
we have had a similar problem with misting on the inside of the car and found that the windscreen was leaking. This caused the front carpets, which have a thick sponge back, to become sodden. After removing them, which is really easy, and drying them, which inot so easy, we could see the water coming in after heavy rain. The leak was traced to a poorly fitted windscreen. this was replaced and problem solved, yee haa.
Top tip, remember to take up the floor plates and dry the puddles.
Enjoy..