Foxxy - of course you can operate N registered aircraft on a British AOC. What do you think Atlas Air have been doing with their 747s leased to BA; and Tradewinds etc with various aircraft leased to UK charter operators?
Really ought to get your facts straight, old chap!
Still, I agree that in the case of the Yanks, their aircraft should be banned from the EU until they allow full wet leases over there.