I have just been informed, by lynx, that Her Majesty's Customs and Excise enter premises, including private dwelling houses as part of their investigations. That they do this without getting a search warrant. This was revealed in a factual documentary called Undercover Customs.
If this is the case I think that's appalling. Any entry should be with the use of a search warrant, signed by an independent Judge. There is no way that law enforcement should be allowed to do this sort of thing with there being checks and balances in place. There is no way we should have law enforcement agencies deciding that they are allowed to breach people's privacy and then just being able to do it, with applying to someone else to make the final decision.