Actually, any child porn sites that the Internet Watch Foundation notices will be blocked too.
The difference between the anti-piracy and illegal porn blocks are that the porn blocks are transparant whilst the anti-piracy blocks are a clear notification page. I'm not sure if that was due to a requirement in the judgement or something else.
I just get a page that never loads for piratebay.se. Far from a clear notification. Then again, I don't use my ISP's DNS.