When you think how so many non-EU registered aircraft drift around Europe and in and out of Europe with ostensibly no definitive 'home base' country, how on earth does a national civil aviation authority within the EASA zone track and monitor who is and who isn't based in their territory of responsibility? 90% of the time, they won't have a clue how to even contact the operator, let alone the owner of such jets with most being on registers of convenience, leased by one party to another, managed by someone else, titled to a different entity etc. etc.
Would love to see the UK CAA try and call up the bloke in charge of that Aruban/Isle of Man/Guernsey/Cayman etc. etc. jet, owned ultimately by a Russian, operated say by some Swiss outfit and spending much of it's life around London, to see if they've declared their Part-NCC compliance - good luck mate! And if they do wander over on the ramp one day at Luton to ask the crew, 'where are you based?' they just say 'USA', 'Dubai', wherever.....certainly not in Europe.