I applaud the UK for researching the possibilities of blocking internet p0rnography, but highlt doubt it is feasable.
This article in BBC: http://www.bbc.co.uk/news/technology-12041063 says that the ISPs being asked to block this crude content is not possible.
Beyond the idea that it's not possible, we get into the realm of 'censorship' and what we here in the United States call 'liberty'. As someone that follows Christ, I don't think this kind of crude and damaging material should have any sort of Constitutional protection because I highly doubt the founders of America would have wanted this material to be protected by out laws.
Never-the-less I applaud the UK government for trying and hope that a similar attempt to curb this nasty medium is in the works.