Probably the UK CMA (Competition and Markets Authority) which regulates competition/antitrust, mergers, national security acquisitions and the like.

Or there is a loosely defined locally-run thing called 'Trading Standards' which is done at the council ("municipality") level.

and for the record I am just being difficult and everyone in tech/mildly well read knows what the (U.S.) FTC is. My point is more that one country's rules don't always matter for the operations of domestic commerce in another amongst their own citizens.

We famously mock our own jusrisprudence - "if Parliament passes a law that it is illegal to smoke on the streets of Paris, then it is illegal to smoke on the streets in Paris", so even when hard legislation exists (4chan/Ofcom shitshow?) it is meaningless.

The only power that matters long term in the universe is sheer force and hard power, and it has always been that way.