"And you?" or "And yourself?" as response to "How are you?"

If someone asks "How are you?", which of the following is grammatically correct?

"I am well, thank you. And you?" or "I am well thank you. And yourself?"

'Yourself' sounds more formal, and is used frequently in everyday language (at least in my surroundings). However, I've been doing a little bit of investigation into the use of my vs myself and you vs yourself and it seems that it is only used reflexively to reflect back to 'you' or 'me' as the subject. E.g., you hurt yourself. In the case of "and you/yourself?", you/yourself is being used as the subject, in which case it would seem that the correct version would be "And you?".

Any clarification on this would be great!

Either of these is fine, although if you're going to use and there should be a comma. The second sentence has a silent you in it, referring back to the fact that it was the original person who asked first and is being thanked.

I am well, thank you, and you?

I am well, thank you, and (you) yourself?

However, asking, "How are you?" may well be derived from an old greeting, "How do you do?"

According to Stephen Fry, the only correct response to "How do you do?" is, "How do you do?". Since Stephen Fry is, of course, the authoritative source of all things English, perhaps we're both wrong.