Actually, just had a go at taking the arm rest apart to find the errant screw that seems to be rattling around....no probs, 4 hex screws and a gentle tug and it was off.
However lo and behold...theres nothing there and the rattle continues...hmmm, the screw must be somewhere else in the centre console....wonder if its in the vents (next place to look and take apart).
I have it booked into the garage but TBH dont want to be without my car for a whole day.