Ford focus 2009 ac not working?

On my cars last service they garage reported my ac isn't working, they checked the gas and said mechanically everything is ok.
I've tried to do a bit of fault finding, i've tested all the relays and fuses all ok. I've tried putting a paper clip in the pressure sensor to force the ac clutch on not worked. Does this mean i've got a faulty ac clutch/compressor or is there something else stopping it working.

You said you "tested" the relay and fuse so I assume you have done that with a test light. So back track the power from the compressor, if you have power to the compressor then it would be the coil if you don't follow the wires back until you get power.

Run a hot wire from the battery positive post and see if the magnetic clutch activates. You can also probe the clutch wire with the motor running and the AC turned on to find out if the wire has 12 volts as it should.Is the condenser fan coming on when the AC is turned on?
If you had a lube joint tell you anything ignore what they said a try charging the system with a can of 134a with the sealer in it. 90% of the time people have a small leak and the system drains down during the Winter.

If its the same compressor clutch setup as various other Fords, there's a shim under the clutch plate that sets the clutch clearance.

As the clutch wears, the gap gradually opens up and eventually it stops engaging properly.
When that happens, you need to put a _thinner_ shim in to set the gap back to what it should be.

Examples:
http://www.ebay.co.uk/...1977485564

http://www.ebay.co.uk/...2120516320

This shows the shim location:
Ford focus 2009 ac not working - 1