Fiancee Visa Obligations

[Wanderer]

If a guy has his fiancee here on fiancee visa - what are his obligations to her, and his legal ones?

Facts are she has a few months left on fiancee visa, they're not going to marry and she says she's not going home, will dissappear to London, work, and eventually go home when she's amassed some cash. She's from Ukr. and her English is poor so I've no idea how she things she's going to get rich.

Aside from castigating the guy for thinking about marrying someone he doesn't know, what are his obligations now? Is he legally liable?

Also can she marry someone else on this fiancee visa?

These hastily-formed internet relationships are making a mockery of the marriage-based settlement visa system, I mean, how marries a person they can't converse with whose face time is measured in days?