Thanks for all the replies.
It was a second half of 2014 build (still digging up the exact build date to confirm Centa compensator).
The bobbins seems fine - no cracks in the rubber pieces and no give on the bolts.
On the drive in to work, I checked for correlation to throttle. It actually seems to diminish/go away with throttle. I noticed it most in idling and at higher speeds with lower throttle.
Richard, thanks for the reminder on the clutch test; I think I have at least removed the neutral rattle possibility, as it is unrelated to clutch engagement.
??? Almost afraid to check the frame now...
