This is false. You of course can regulate and fine a foreign business. That's how trade regulations work.
The UK isn't going to get a cent from that but the leadership is banned from entering the UK for the foreseeable future.
Doing this a lot as a country is how you achieve pariah status and losing a bunch of trade, though.
Trade regulations apply to the importer, which might also be the exporter if they have a local presence, but also may not be.
If I buy something illegal off of AliExpress, the US government won't and can't do squat to the seller. If they decide to enforce the law, they'll go after me.
> the leadership is banned from entering the UK for the foreseeable future
Not at all. But if they do enter, they might find difficulty leaving.