Sure, but to what extent could they operate without upsetting the UK? Some tax-free tourism? Probably get away with it. Running some sort of Epcot/Sidewalk Labs

Sure, but to what extent could they operate without upsetting the UK? Some tax-free tourism? Probably get away with it. Running some sort of Epcot/Sidewalk Labs-esque experimental town on "land" nobody cares about... probably also workable. As long as it doesn't pose a danger to the UK and isn't distinctly criminal in nature, it's probably not going to get much attention.