I'm pretty sure it's suspension related.
Although it passed its MoT a few months ago, it was in A for Audi recently for it's therm' problem, and they mentioned 'straight arms and drop links worn' on the report.
Sounds plausible to me and car going there on Friday.
Just wanted to see if A8 Parts folk had different ideas, beacause it could easily be something else!
I'd hate to spend a bunch of lolly on these suspension bits (albeit they are clearly worn) and find its still got the clunk.