I'll be doing a few of these summaries on different countries on what sort of Internet censorship happens in various countries. Lets start with a fairly uncontroversial one and that's censorship in the UK.
Well if you live in the UK you'll be pleased to know apart from the worrying fact that as in most of Europe - your every move is logged and backed up at your ISP for up to two years, that is little actual Internet Censorship in the UK.
The only censorship is enforced by the UK government and is usually by the two main software products - 'clean feed' and 'webminder'. These are content blocking systems which mainly work on an IP black list and are used to block web sites and pages which are believed to contain indecent photographs of children.
They are run by your ISP and if any such page is attempted to be accessed then a 'url not found' message will be delivered to the client rather than a warning.
It's not the most fantastic system out there as it does make mistakes and it is rather trivial to circumvent e.g via a proxy server.