Vauxhall Astra no air con

My air conditioning is not functioning. I have confirmed visually that the clutch is not engaging onto the compressor and I have used a multimeter to determine that there is no power going to the clutch solenoid.
All fuses checked and functioning. Internal air con button is lighting up when pressed. System gas pressure is good and was checked by a local garage today. I suspect a relay but can find no information as to its whereabouts.