just had a look at the chilthurst domain, at £2.95 per email !, that's £35.40 per year, wow that's a lot considering your email is free with your isp, no wonder no-one signed up. some ideas :-
1) offer the email address free for the first year...with small print blurb (terms and conds) on the flyer/website that 'we are offering this exclusive offer to Chilthurst residents as a free service however if demand increases along with bandwidth we may have charge a small fee (approx £2.95 per year) to accomodate the extra demand'
now people will sign up if it's free (I would), let them use it for a year , give out email addresses, get comfortable with it, etc and then hit them with a email about the demand and the £2.95 per year.
£2.95 x 92761 (population source google)= £273644.95
2) integrate voucher/freebies deals exclusive to chisleton folk (see
http://www.hotukdeals.com/vouchers-static.html)
3) how about a shoutbox for people in your street (or user specified),when someones online.