it’s a tough one. i dont think you can rule out the London vet because he is strict about the age thing; did he explain why that’s his policy? i know that the lady at my local pet-shop who’s ‘qualified’ in these matters (though she comes from a strictly academic pont of view- she believes rabbits are too smelly to be house pets) told me i should wait for a few months for Lollo’s hormones to settle which would have taken him up to about 6 months. having ignored her, i have no doubts i was right, but each situation is different and i think the vet should be willing to look at each case on its merit like mine did.

my vet has her own rabbits so when i phoned up to enquire initially the nurse spent a lot of time explaining how good harriet is specifically with rabbits and the sorts of things they deal/ have dealt with. this really helped.

if you haven’t found a more local vet that you trust he may be the best option BUT i think its a good idea to find a local person you can trust and that can build up a knowledge of your bunny so that if there is an emergency ever you know they are clued-up and have the history to hand.

the (whichever) vet will do an initial check to make sure bunny is fit enough to go through the operation; i’m sure once you’ve made the decision the initial meeting will put your mind at ease at least as easy as it could be in the circumstances!

Did the vet say exactly why.   I mean did the vet just make that arbitrary date, or was it after an exam?  Have Dougals testicles dropped yet?  IF not, then maybe that is the reason for the vets decision.

I know it must be scary.  I think one of the ways to help you find a good vet is to use the screening questions.
http://www.rabbit.org/faq/sections/vet.html#questions