Had A/C filled following the major "service", which included a new compressor, condensor, drier and microswitch (all sourced relatively cheaply on ebay), and I have properly cold air again and no reported leaks

The compressor is quite noisy at idle when engaged the noise goes away with increased revs, but sounds like one of those single piston air compressors at idle, not quite sure why or if there's anything that can be done about it, anyone got any ideas? We checked that it had oil it it before it was fitted.