What happens to Tom Quinn on mI5?

Answer 1

He probably went back with Elle and got a job with some private security agency; he'll probably guest star in a later episode, where he and MI-5 fight it out, and they force him to leave the country, or he gets killed. Alternately, he could've defected, although that's unlikely. If he went back to work for the government, MI6 is probably running him as a sleeper, or to use him to get dirt on MI5. Dozens of possibilities, maybe he works at a supermarket. Hahaha-nah, he's probably doing something cool that pays good money.