2010 Mazda 5 Broken Aircon

[zedx19]

Mrs zed has a 2010 Mazda 5 2 litre petrol, which we bought cheap with non-functioning aircon. I took it to a very helpful local chap for a regas, hoping that was all it needed. He did his checks, told me there was zero gas in the system, leak checked it fine so refilled it to the correct level. The aircon still doesn't work and there's no click when turned on, however the engine revs do rise when it's turned on now and the fans kick in. Aircon chap suspected clutch or pressure valve but does anyone have any idea which it might be? I find it odd that the revs rise and fans kick in now, as if somethings happening but no cold air arrives and no click from the motor.