Easy. You call up the US vendor that sold China their Great Firewall and order another one. This one will be cheap, considering the UK's population is a fraction that of China.
Already done: TalkTalk (arguably the UK's worst ISP in general, as well as being the first to jump on the government's bandwagon) spent many millions of pounds (described in a related court case as "an eight figure sum") importing a horribly flawed censorship system from Huawei, which is one of the Chinese manufacturers of part of the Great Firewall.
A few principled UK ISPs are standing up to censorship, and still offering unfiltered services - though I do fear Cameron will attack them for it now: like most bullies, he can't handle criticism or opposition.