Well, blow me down if I haven't just had a positive experience with a GP about an injury!
I happened by pure chance on one who is a runner himself, who listened to me and didn't just give me the standard "rest it till it doesn't hurt any more" response. He didn't really want to give an answer on whether it would be OK to run 5km on it in 2 weeks' time (not that I'm going to be fit to do that, mind you, but it would be nice to run some of it at least), but did say that while he wouldn't recommend a marathon, 5km wasn't all that far really, was it, and if it was something I really wanted to do, then why not go for it.
He's given me a load of exercises to do and we even had an interesting chat about the benefits of supportive shoes vs going barefoot, or nearly barefoot. I didn't even bother to ask for a physio referral as it was really exercises and a way back into running that I wanted and he's given me those.
It was an excellent experience all round, in fact, as my blood pressure has dropped enough to be called normal (which it hasn't been in a long time - it's got to be thanks to the running

) and I got the results from a blood test which also showed everything normal and a cholesterol level which "lots of people would give their eye teeth for".
Now I just have to find some marbles to pick up with my toes...