Thanks for your replies.

Since my partner's already got a visitor visa and there's no administrative reason to get married in the UK, I think we'll get officially married in Vietnam and then register with the British Embassy.

Hello. I'd appreciate some thoughts about this: I live in Vietnam. I'm planning to marry my Vietnamese girlfriend. We're wondering if it makes any difference whether we get married here and then register it with the British Embassy in Hanoi, or try to get a marriage visa and get married in the UK ...