Isn't there already an opt out porn filter in the UK?

Only on mobile devices usually. I had to opt out to look at the thinkpad wiki so you can see how well that works.

And I thought it was just me for thinkwiki.org... why on earth is that an adult website?

Probably a shared host. All the other sites are porn.

Which makes the point about how ridiculous recording an IP address is.

I some how doubt that thinkwiki is on a shared hosting.

Tons of developer/security websites are blocked on O2 "hacking tools"....

They are using the same nonsensical lists that some web gateways use, anything that is even remotely objectionable is blocked.

Same on freebsd forum.

Even worse as that's about as legitimate as it gets.