How I react to personal comments depends on a lot of things - the circumstances (ie. people shouting insults at me in the street vs. conversations on tube platforms), my general state of mind (if I'm startled I'm going to react very strongly) etc.

I didn't feel particularly threatened because we weren't the only two people on the platform and he was on a bench at the opposite end of the shelter. I did make sure we got into different carriages when we got on the train though. But yes, sleazy men ---. Why does no one teach them that it *is* rude to ask questions like that even when prefaced with 'I don't mean to be rude'?