I can remember how the old DTI (forerunner to Ofcom) took a lot of action against Laser 558 and Radio Caroline for pirate broadcasting in 1980s, in spite of neither being fully UK based (but both easily receivable in Britain).
Their owners claimed it was a "fun" project but both stations took advertising, and Laser was once partly funded by Philip Morris cigarettes and intended to get round EU-wide restriction on tobacco advertising (not the first time offshore pirates had done it). In the end the whole EU leaned on PM to pull the funding (and Laser eventually ran out of money not long afterwards)