My fiancé and I are meeting in NYC to be married and then I'm planning to move to England to live with him. Since it's a same sex marriage, is there a visa he'd have to apply for, for us to get married other than the visitor's visa? I want to do this completely legally so that we don't get into any kind of legal troubles.

A tourist visa is all that he needs.but, many residents of the UK for a short visit of 30 days or less do not even need a visa, there is an international agreement among many nations allowing short stays without any.

Visa Waiver Program | Embassy of the United States