i  live in kent and have read about vasectomy for dogs but i can not find out how to find a vet my vet thinks i am mad could anyone help me

Have you explained to your vet your reasons for wanting a vasectomy over a castration?  And what are his reasons for thinking a castration should be performed?  Many trainers these days are actually geared up to helping owners through the worst of the 'teenage' years with adolescent dogs, and the resulting adult dog often has fewer dog to dog issues as an adult.