Would this still be possible if its true at all ? surely the British military would come and overthrow you.
http://en.wikipedia.org/wiki/Sark#Oane-person_invasion_attempt
In August 1990, an unemployed French nuclear physicist named André Gardes attempted a singlehanded invasion of Sark, armed with a semi-automatic weapon. The night Gardes arrived, he put up signs declaring his intention to take over the island the following day at noon. He was arrested while sitting on a bench, changing the gun's magazine and waiting for noon to arrive, by the island's volunteer constable.
http://en.wikipedia.org/wiki/Sark#Oane-person_invasion_attempt