Further to my last post I was doing some rooting around in the boot liner to see if I could find any water in there.
I opened the panel that houses the warning triangle, just behind the number plate, and managed to break the catch that holds it in place. Seems it was very brittle or something as I didn't apply much pressure to it.
Anyway, it's annoying me now (i don't like anything to be broken or loose in my car - it really gets to me!) and I'm hoping someone will have the part I need from a non-runner.
So, if anyone is breaking an A6 avant (circa 2004) for spares, or simply has the part I need kicking about, I'd be grateful if you could get in touch.
Thanks in advance!