I'm sorry, but only our popcorn will work in this theatre.
I'm old enough to remember the pre EU days, and boy was that a racket for UK businesses. Having a specific UK weirdness about a product ensured no foreign competition got a look in and the British consumer paid dearly for it. The UK standards were not at all terrible, in fact some were quite good, but they did ensure consumers got their wallets rinsed at every stage, so yes, businesses far and wide would be looking to return back to the days where a specific demographic can get scalped, while other players get squeezed out due to the costs of regional compliance.