Thanks guys.
I've been wanting to release him for a few weeks now, but the plot steward asked me to hold off so that we can organise a bit of a 'thing' and get the local rag to take a few photos - fair enough, I'm all for that, but I think he was getting restless.
Funny thing is that for two or three weeks, he's been opening the hutch (goodness knows how), having a mooch and then settling down back in the hutch (which, I hasten to add, is four feet high, on top of another hutch!)
This time, I think it has dawned on him that there's a bigger world to explore!
He was about 250 grammes when he was found and I managed to get him up to 350 in a few weeks but not in time to release him before the winter hibernation, so we kept him indoors for a while and then 'hardened' him off by putting him in a 'hibernation hutch' on the plot, in a fairly sheltered and quiet spot.
Sure enough, he went into hibernation and we just hoped for the best.
When he came out in March, he was badly underweight and in a real state. I put him on a diet of regular, small amounts of fresh water, eggs and... fat balls! Once he gained some weight, we changed the diet to eggs and mealworms (with the very occasional fat ball treat).
I'll probably be lambasted for the diet, but it worked!