well, she's booked in for the check up with Benny on Saturday so I'll keep my fingers crossed that all goes smoothly and it's one of the few that were fitted with the fixed parts. I know it's a late 2003 model but that only means it was sold then, when it was put together in the factory, who knows.
Gonna keep the balancing chain in mind but, tbh, it's doesn't really sound like a chain problem. The noise is, after all, a "tick, tick, tick" rather than a "clang" that I would expect from a loose chain. either way, it shouldn't sound rough at all. Not a 2.2 engine with 31k on the clock.
Thanks for all your help, i'll report back. Wish me luck.