I didn't think ning was allowing adult sites any longer.
Buddypress has promise - I've been using it for a few months on tow different domains - but it sucks. No photo gallery, no chat included, groups are lame. I love WP - but Bpress is probably another year (or two at this rate) from being ready for actual live site deployment.
I saw this script:
http://directory.javier-garcia.com/ running another adult site today - there is a free version. From my 2 minutes of surfing it looks promising.
You are the best php programmer in uk huh? I may have some projects to send your way.