R50 2002 - Air Con not working - No power
 

Have an R50 Cooper. Aircon has not been working for last 3-4 months. Went on vacation it was working. Parked it up while away (only a week) When we got back aircon was apparently dead as was the rear demister/defrosting switch. Both remain non functional and I have checked all the fuses I can find (LH footwell pillar and under hood/bonnet alongside battery enclosure.) More?

Any thoughts as to the next steps? I am thinking Relay but what is the best/easiest way to test. Why would the A/C be related to the rear window heater?

Any help greatly appreciate