It's not a case that one domain = one site ranking. If you look at the backlink profiles for the ones that are ranking they're using the domains they buy in a few different ways:
1. Core site to rank for the main term (mainly non-gamstop, although they have been creeping into the generic terms as well)
- eg: mentoruk.org.uk
2. Redirects into the core site (although I guess these could have been ranking sites that were moved)
- eg: thebackbencher.co.uk
3. Rebuilds of an expired site with a sitewide link to the core site using the target anchor (there are tons of these per site)
- eg: glastonburyfm.co.uk
So it could be that for every site you see ranking they're actually using quite a lot of these domains to do it which is why they're so hungry for them.
That and stopping their competition.
1. Core site to rank for the main term (mainly non-gamstop, although they have been creeping into the generic terms as well)
- eg: mentoruk.org.uk
2. Redirects into the core site (although I guess these could have been ranking sites that were moved)
- eg: thebackbencher.co.uk
3. Rebuilds of an expired site with a sitewide link to the core site using the target anchor (there are tons of these per site)
- eg: glastonburyfm.co.uk
So it could be that for every site you see ranking they're actually using quite a lot of these domains to do it which is why they're so hungry for them.
That and stopping their competition.