They do if they are libertarian governments. Although it's popular to pretend they don't exist, there are plenty of examples of governments reducing their power over history. The American government is a good example of this having originally bound itself by a constitution that limits its own power. And Britain has in the past gone through deregulatory phases and shrunk the state.
Unfortunately at this time Britain doesn't really have a viable libertarian party. Reform is primarily focused on immigration, and the conservatives have largely withered on the vine becoming merely another center left party. So it's really very unclear if there are any parties that would in fact roll this back, although Nigel Farage is saying they would. His weakness is that he is not always terribly focused on recruiting people ideologically aligned to himself or even spelling out what exactly his ideology is. This is the same problem that the conservatives had and it can lead to back benches that are not on board with what needs to be done. Farage himself though is highly reasonable and always has been.
