I too have tried to do a national site with my domain
www.ukwhatsonguide.co.uk. It's extremely hard to do if you are unable to do it full-time! Maybe take a leaf from friends reunited and go for it! My focus however is purely on getting my domain up the search engines at present and allowing people to enter data for free. The rest will come later. The more things we put on the site, the more likely we are to get found! If you search for 'what's on' on google.co.uk (UK sites only) we are front page!
Loads of people search for car boot sales (i don't get it!) so worth listing these on your site?