[ColinWright]

Everything I'm reading at the moment suggest that this is not the case in the UK. Apparently as of about now, ISPs are turning on filtering by default without asking, and you must explicitly contact them to get it turned off. People I know who use O2 are, without being asked or contacted, finding that sites are getting blocked.

Some ISPs are, apparently, asking for explicit confirmation with a phrase such as "So you are requesting access to sites that carry pornographical material", and if you want to access anything that the Government has decided to block, you must reply "Yes."

I have no doubt that lists of people who have opted-out will, at some point, be leaked.

[desas]

When signing up for fixed line broadband with any of the biggest ISPs you have to make a choice between filtered and unfiltered. As the GP said, mobile broadband has filtering enabled by default and has done for years.

Source: Am in the UK & have opted out of filtering. All fixed line ISPs allow toggling the filter bias their online control panel, or by clicking a button when signing up online. Mobile ISPs vary - O2 mobile require you give your card details.