Yes, and?
Countries, including America, have investigatory rules where you are not allowed to talk about it at all. Want to do business in a country? You need to obey their rules. And you don't have a leg to stand on complaining if you have similar roles because then you're not saying the rules are morally wrong, you're saying you're special.
It is absolutely not improper for the UK to do such a thing and the US would have no qualms about using a national security letter (is that the right term?) on an American subsidiary of a UK company. It's how laws and jurisdictions work. Having a foreign ownership doesn't give you special dispensation to break a country's laws. Apple UK are absolutely subject to every single one of the UK's laws. They're also subject to quite a lot of American ones, having an American owner, but that's their problem not the UK's, and doesn't give any special treatment other than what America can force on the world under the universal law of might is right.
Note this is all orthogonal to what I personally think of the RIPA (my quite strong opinions are in other much older Slashdot posts).