Mines been fine for 300 miles, until today. I have air escaping from the compressor area, as the compressor starts and stops I can here PSSHHHHT a bit like when you remove a tyre pump from a valve.

I think it only does this as the compressor starts and stops although not sure, at first I thought it may have been a HGV behind me but it did it again on the way home from work.

Could be air escaping from the output air line, or something else. Everything is still working, no fault codes. I'll give the mechanic a call tomorrow I guess.

Probably just an airlock somewhere? The compressor might auto bleed?

The mechanic is popping by my workplace on his way to work tomorrow to have a listen and take the car if he thinks something is wrong. I hope the sound can be replicated on demand.

To confirm, I can replicate it on demand, it appears to be as the compressor shuts off. If I sit in the car and select Lift, so the car uses the air in the tank, then select Dynamic so the car dumps all the air from the struts. Finally select Lift again, so the compressor must run to get pressure back. After the car has raised and the pressure tank is full, the compressor cuts out but just as it stops there is a psssht sound lasting just a fraction of a second. Does it every time, so I can show him tomorrow morning.

The sound maybe normal, but I can't say I have noticed it before.

He has been, and has taken the car back to the workshop. He is happy that something is not right, so will once again gain access to the compressor. Compressor is working fine, but air is escaping from the compressor area when its running.

Maybe it is purging/regenerating the air-dryer?
"The appropriate valves 9a, 9b and 9c, 9d and the electrical exhaust solenoid valve 5 are opened. The air can flow through the exhaust solenoid 5 to open the pneumatic, pilot operated exhaust solenoid 6.
The air leaves the system via exhaust solenoid 6, additional silencer 7 and air filter 8. When air flows through the air drier 2, the desiccant is regenerated."

The sound is quiet loud though, I am sure it must do this in normal operation, pehaps damped by something. I could here it pssshhht as he drove out the car park.

He did the repair last Tuesday, and it was silent on till Sunday night having driven the car for around 5 hours in total during the weekend.

Well all seems ok after my repair so far. All functions there, no compressor banging. The front looks high however, and I'm convinced the ride in comfort is firmer than it was before... Anyway, I'm not complaining I just hope that all is now well.

It's a stress all this air ride stuff... Completely just expect it all to go wrong!

Sounds like you need a recalibration Jonk. VCDS you can do it.

Guys, how much did the whole repair cost you, parts + labour??
Just out off interest, it could be a good preventive maintenance which I could consider doing as long there isn't too much risk and fragile parts or procedures.
Cheers +++