Hi,
About charges, I was thinking along the lines of free listings, trying to figure out the best approach for that.
One idea would be to offer two levels, basic listing - no link required, the other would be a Premium link which would have a banner, live screenshot of site, live mapping, client form for bookings etc etc but link required. If link is removed, the link would automatically be dropped.
Now, what we could do is offer adds say, 468 and 120 ads which would relate to a specific town or city for a annual fee of x, ads to cover that complete area, and global ads to cover the whole UK etc.
I need a few banners 468x60 and 120x600 to test this idea out so if anyone is interested me me know.