After putting another power steering pump in the noise was still there. You can imagine - the swearbox got a filling! I decided it might be the fanbelt and set about changing it. The one I took off looked perfect.
So no progress.
When I got the pump from A8 parts (great service) I got an A/C compressor just in case that was the problem. Because I did not want to lose the gas and had no Idea about how or how much oil to put in I was a bit reluctant.
After studying the electronic manual I was given, there are a few servicing jobs you can do on the compressor without fully disconnecting it. There is a fair amount of play in the pipes that allows you to unbolt the compressor and lower it down. While up on the ramps it wouldn't reach the floor but I used a toolbox underneath and it was perfect. When I compared the 2 compressors, the magnetic-clutch bearing was a bit loose on the one on the car.
It was a simple job to swap over the pulley and bearing from the spare I had.
Bolting it back up was easy and no re-gas required!
After a nervous start - noise now gone!
If you get the same noise you might want to give this a try.
Martin