The forum I found with my Passat was this one:
http://www.vwaudiforum.co.uk/
It's a good forum.They have their own version of Arctic, called "Crasher" who is an absolute guru with 35K (yes, you read that right!) posts.
There are several others but the earlier posts are a pretty close description to their content
For cleaning/valeting/detailing there's the one several of us on here are on:
https://www.detailingworld.co.uk
Our forum is, of course, the best
.
Andy.