You've just said it yourself, though. They need a warrant to search your house. The same should apply here.

Yeah, like I say there should be reason for doing it, so getting a warrant of some sort based on whatever reasoning they have would probably be best (although they don't need warrants for things like stop and search which is also an invasion of privacy, the house searching was just one example)... we already have our privacy invaded in a number of ways it's just not so prevalent in the online world and I think that's more just to do with security services not catching up with how the world has changed over recent years rather than it being because those things are very different in principle to how they already investigate people and situations.

Law Enforcement of any kind should only be able to access someone's online details if they're really suspicious that the person is up to no good, other than that then they should stay out of people's business on anything else.