FAA registered aircraft
Just because they are on the N reg doesn't mean they are flying illegally or doing AOC work, i think most people seem to have it in for them, but personally i find most of the brits are ill informed, its the CAA that have got it in for you, most helicopters over the years have been built in the US and generally i think they know what they are talking about, since they designed it, built it, got it approved all but for the CAA sticking there two pence in with often unessary mods that are now disappearing with EASA.
Enjoy your flying and with any luck EASA might improve things.