I have access to several machines on UK ISPs. Quick SSH and poke with links on each machine.

1. Easynet - all work fine.

2. Andrews & Arnold - all work fine (this is expected)

3. O2/Sky - all work fine

4. BT - all work fine

All of these lines were provisioned before the porn filter was announced so...

Edit: tested Amnesty, OpenBSD (which these machines are all running and would be a PITA for me) and linux.com