Thought i would just post a quick note here on topping up aircon, Ive been on a gas safety course for Aircon gas today and if your thinking of topping up with the little cans they sell in Halfraudsand the like basically DON'T
the guy doing the training has seen a couple of car aircon systems where these were used and they caused moisture in the aircon system to explode in the condenser causing obvious damage etc and a big repair bill
If you think your aircon needs topping up get a professional with all the kit to check over the system properly and safely