I can see a Sealand 2.0 spring up around the launching of rockets from international waters. It also looks as if the bulk of the regulatory reason here is the use of the radio spectrum and not the actual launch.
The UK basically rolled their eyes the same way they'd ignore a kid declaring their backyard tree fort to be sovereign territory. If they'd started launching rockets, that might've been different.
Would that simple fact not incentive you to question your assumptions of either the burden of regulation, or the possibility of end-runs around the law with cheap stunts, before furthering this strange case of “jingoism with no nation”?