It's been a week of things breaking. I got a new chainring, chain and cassette fitted on Tuesday. On Thursday there was an almighty clunk as I was pulling away from traffic lights (quite hard), the chainring ending up sufficiently bent that it couldn't reliably hold the chain anymore. Fortunately I have three front sprockets and the bend wasn't sufficiently bad to prevent it rotating, so I could use the middle ring to get to the bikeshop on Friday.
Then my boiler broke, it's been noisy for a while and got increasingly dodgy over the past couple of weeks. I phoned up a gas fitter, who came and fitted a new fan (which wasn't cheap).
Today my Windows installation broke with a corrupt registry file. Looks like I finally need a re-install (chkdsk /p from a recovery console didn't help).