guys.... DO NOT use that stuff! I attempted it yself and bought a duff can, so I went back and MR KNOW IT ALL HALFORDS assisstant said that he would do it for me. However when he finished he said "ah thats strange your compressor has stopped working" which was working absolutly fine before he touched the car, as it was the first thing he checked.
To cut a long story short took it to a garage and the fault was diagnosed as the muppet from halfords over filling my aircon system, and as a safety feature the compressor won't kick in.
Cost me approx £70-90 for a aircon clean check and regas at the garage.
When chatting to the air con tech he told me that those cans are a bad idea, and verging on illeagal as you have to be licenced to handle refridgerants and disposal etc.
In my opinion it's a massive rip off and I'd steer well clear, it's well worth gettin the job done properly doesnt cost much more