We've had someone travel from France in the past! You should have told us in advance and we could have reserved a prime seat right up at the front for you.
There are typically quite a few people from Brighton and Cambridge who come along. We usually finish at around 10pm so there is scope for getting the train home after.
The furthest that people have traveled just for the event (that I am aware of) is from Paris.
I'm unconvinced that Bristol (or any other region of the UK, especially those commutable to London) has the critical mass necessary to support one. Perhaps a worthwhile experiment though.
Well, there are two MS/.NET usergroups in Bristol, one of which has had 100+ people in attendance a couple of times and there a few other user groups in human factors and such.
London will always be the exception, but given the number of user groups already held in Bristol that manage to get around 50-100+ people in a month with ease I think that Bristol would be the natural choice outside of London.
Whether a HN meetup would be successful or not is another story. It'd be entirely down to who would choose to organise it and what they could offer to local HN members.
IIRC it was 15-20 in Songkick's original offices at the back of Spitalfields market (although physical size wise it was probably about the size of a living room), it frequently over-flowed into the corridor.
They used to make everyone introduce themselves at the start, modern HN meetups lack that sense of intimacy :)
I'm in Bristol, so a bit far to travel.