ive got no air con so i went to halfords and got the gas to top it up and it came with a gauge.
gauge says its full but ive still got no cold air coming out
any ideas
ryan 
Had the same thing on mine about 18 months ago, Does the air con compressor start when you switch on the air con, if it does as mine did then check the flap operation in the car, i found that when i switched the climate to cold it would only blow hot, it turned out to be a failed flap servo (It opens and closes the vent flaps in the car).
It was stuck on hot air circulation.
The servos are under the centre console at the front on either side of the footwells, not easy to get to but when you remove the lower trim you will see the small servos attached by ball joints to plastic arms, the arms push the flaps, the ball joints are what fail, thus not opening/closing the flaps. (try operating different vents as you watch the various servos, as said its not easy, ask the other half to help)

The above is for the facelift Omega (climate control), i am not sure if the servo set up is the same on pre facelift. I am almost sure there is a topic on the air con servos in the tech side of the forum.
Hope this helps