Skoda Octavia II - Air Conditioning sounding like an old fridge - RDJH

Anyone have an idea as to why the A/C on my 54 plate Octavia II has started to sound like an old fridge. Two very distinct noises, one a gurgling sound which is constant when the A/C is on the other a low hum which comes and goes but can be felt as a vibration through the dash centre panel. Both of these can only be heard in the car as engine noise outside masks them and stop when the A/C is switched off. I am hoping it is not a compressor as that looks to be both a common and expensive problem.

rob