I have seen similar threads and decent activity on UKWW. I have been active on other forums but UKWW has been most successful in building a community. Till last year v7n was a good option too, but the forum is going downhill
May I know what is UKWW? I also agree that v7n is going downhill, and it mixes the link sale with the link exchange together.
That's ukww: http://forums.ukwebmasterworld.com/ For every buy request you don't receive as many responses as you do on DP
You can try dofollow blog commenting. Basically, you cannot buy or sell PR link (dofollow), it might get your url and your link seller pr to get penalized.
But if you sell your PR LINKS in text-link-ads.com.. The price from text-link-ads.com is very cheap..