Re: They might consider
@Yet Another Anonymous Coward
[ Re: pursuing compensation for the emergency services. ]
" What's the cut-off? "
I would say that performing a stunt in a professional capacity without a completed form signed by a suitably qualified risk-assessor and without the requisite safety equipment on-site is already illegal. And not warning the emergency services and/or the local council in advance of a potentially dangerous stunt too... but as the notification would have needed to include a risk assessment form, they wouldn't have been able to do that anyway.
The problem here is the way the so-called "gig-economy" takes amateurs and pays them, but still treats them as amateurs.
Sunday-league football, skiing, skydiving and cycling are mostly amateur affairs. Professional sports, on the other hand, are generally expected to have medical and crowd-control staff on-site, and are generally expected to pay for that.
Road racing on open roads is illegal, so I'll assume you're referring to closed-road events, where the organiser is again responsible for maintaining suitable response provision just in case there's an accident.
Rocket-powered cars for TV... well, again, TV has health-and-safety obligations. However, I do believe it's a bit of a different question whether you're talking about a competent professional racer like Guy Martin or a hyperactive middle-aged-"lad" TV-presenter like Richard Hammond. Top Gear was highly irresponsible letting Hammond go in that thing, and really the show should have been closed down permanently at that point.