Well I've noticed that a lot of fans of the series are from around Liverpool - but certainly not all. If you look through the posts on the guestbook they are from all over the world in fact. In my recent visit to the UK I hooked up with a few other fans including people from London, Leeds, Hull, Tredegar (South Wales) as well as a fellow (ex)Australian. In fact now that I think of it no Liverpudlians! - aren't you guys sociable or something??
Personally I was 14. It does seem that the most common age for obsessed fans is 12-18, but I also know a number of fans who were in their 20's. In fact one of the earliest visitors to the site was an Australian lady from Melbourne who is now in her 50's, so I suppose in her thirties back then.
It seems to be a common assumption that the series would have appealed only to those intimately familiar with the subject and location, but I think all that was needed was an understanding of the emotions.