Networking question: hanging out together

I've recently contacted an analyst at one of the BB's in London. We had a phone conversation and he answered a lot of my questions, we laughed a bit and in general it was pretty good and fun.

Now I am wondering if it is ok to ask him to hang out together on Friday evening or on weekend or to have lunch. I'd like to do this because I think that it will be easier to get along and build rapport if we meet in person rather than keep e-mailing each other.

And another question: is it ok to ask an associate to hang out together or have lunch or will it be some kind of a violation of etiquette?

Thank you in advance.