Ok, so I looked at my SO.com accounts tab and it said I could associate my account with my meta account. Strangely, it said there was no serverfault account to associate with, even though I have one and all three accounts authentiacte using the same provider - Google.
So now my SO profile says I'm happily associated with meta, but my meta profile says I'm not associated with anything. Trying to update my meta profile with my email address says that the address is already registered to someone else.
Meanwhile, serverfault knows my email address but then happily prompts me to associate with both SO and meta, despite SO telling me it can't associate the other way round.
Quite a pickle.
Where has it gone wrong? Is there anything I can do from my end to unwind this tangle?