From what I can gather, a re-gas from somewhere like kwik-fit is around the £40 mark, main dealer £80-£100. The only problem in the main is the fact that for the system to need re-gassing, the gas must've escaped somehow, which generally means a leak. At a professional place (I'll let you make your own choice on kwik-fit ), they will add a dye which will highlight any leak points. If you buy your own cans (which you can get from halfrauds I believe), this will not be the case. The other thing is that the pro re-gas will suck out any air and moisture first, which you wont do yourself, which can just introduce other problems. As Mike_Mac also mentions, o-rings perishing and/or hardening is on of the more common leak problems. The less you use the aircon, the more like this is to happen.