Took me long enough, but I finally got to fixing the problem. Had the extra disc lying around for a while but just didn't get round to fixing the problem. It's warmed up a bit around here and the problem was less obvious while my schedule was properly full. Problem got worse however (last week was HELL, stalled a number of times in the most inconvenient places), and I really couldn't postpone the operation any longer.
Had I known fixing it would take 10 minutes, I'd have done it earlier, obviously. The "it's the belleville spring" crowd was 100% correct. Seriously groovy stuff.
Took a testride and it's sweet as a nut again.
Thanks guys :)