I've had an offer from Oxfam, which I've decided to accept. The salary is a bit of a compromise: not as good as I was pushing for, but there is good mitigation for that.
The feedback was that they really liked me: they thought I would be a good personality fit for the team, they liked my attitude and approach and my interest in non-profit organisations. They were also impressed by my presentation.
The downside - and why the compromise over salary - is that they had other candidates who had better technical knowledge. This is totally fair. I always knew that my rather aging technical knowledge - due to working at one company for a long time where they have a fairly stagnant technical stack - would be my weakest part. But it seems that it was more important to find someone who fits the team than to tick all the boxes technically.
I'm quite ridiculously pleased with this result. I'm not telling everyone yet (so I'm talking about it here on LJ, but not on Facebook) until I've got the official offer and sorted out the admin. We're also working out a start date - as next week is a bank holiday week, I've put in a bid for earliest starting date of 6th June.
So there will probably be an epilogue at some point, but in the meantime I am a very happy bunny!