UK Car Repair Questions? Ask a Mechanic for Answers ASAP
I am sorry that you have not been helped yet. I just came online and saw your question.
The most likely cause is the AC compressor clutch coil shims coming apart or the clutch coil it self coming apart. It would help to verify if I could listen to the noise. If you have a phone that records video and audio, record it, upload to youtube and post a link here for me.