My 360 turbo has developed a bit of a clutch groan sometimes when engaging or disengaging under a bit of power. ie pulling off or downchanging using engine braking.

This seems to have happened after changing the friction disk to the part used Vauxhall plate, but I can't imagine its anything to do with it.

At the start its had a brand new (NOS) Volvo 360 release bearing and a new pilot bearing. I'm probably going to put a new disk in at some point (when it comes in stock) as the old one seems to be a bit loose in the takeup springs, anyone have any expereince with this. Likely to be one or other part?

So this was the cheapo ebay used clutch plate causing the groan. The pilot bearing was fine, perfectly smooth in operation. All fixed now.

I waited for months for the Amazon advanced order for the Sachs plate to be supplied but it never happened, so I had to buy a full Astra GTE kit at 130 or so (Plate was 116 on its own). Seems the plates are very hard to get, getting to the point of being worthwhile paying the 170 for the uprated ones from Helix or similar. Hopefully I can get something back on the Astra bearing and cover plate.

Didn't someone say the mk3 golf GTI clutch fits and is 228mm?

Check ZF webcat, not seeing GTI stuff, but there are a number of years/options I only checked 2.

The VW transporter has the same spline number and 228mm dia and I have heard people mention it. Whether the thickness is good or not I don't know, the Audi one are too thick and not much space for shims. The Vauxhall one is for a high performance application so might be better.
SACHS 1861 581 437 has A few hits on ebay

There are a number of other hits where aftermartket replacement might be availble.