I think that in many cases the US intel community is willing to cede way to the British one only because the Brits have been spying on peopl and interfering in peoples' lives much longer than the CIA have. The British empire was built on spies and intrigue, and although it sounds cliche, the British have always evinced a more subtle - and more deadly - hand in the affairs of espionage than have their colonial cousins in CIA.

Also, we should remember that the United Kingdom is not the USA (duh). As a monarchy, the British government and its spy agencies enjoy much more power and secrecy, and much LESS oversight and accountability, than do their American counterparts. Take the Official Secrets Act, for example. The US has no analog to this because it would go against the US constitution.

In short, there is no "Bill of Rights" in the UK, and there could never be any Uk version of the Church Commission, because, after all, it is "Her Majesty's government", and not the peoples' government.

Indeed, although we like to think that the US and UK are alike in terms of citizens' rights and public oversight, that is not the case, and MI6 can "legally" get away with a lot more than can the CIA.