I think you would have to define a “grey importer”. I’m fairly sure it used to mean a U.K. based firm selling stuff they imported privately without going through the manufacture’s official importer whereas now it seems to refer to a firm based overseas.
I expect the first kind did pay/charge duty & tax whereas the second type pays, as you say, all they are liable for, which is nil as the final customer (you) is the importer. They do cough up on behalf of the customer when they get caught red-handed because it a cheap way to do business

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I think this has all been done to death here many times before. I suppose the smugglers feel guilty and want reassurance from their fellows

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The only smuggling I’ve done was pre joining the “EU” with fags, booze, salami and cheese in personal quantities. I never felt guilty but rather enjoyed following the ancient tradition of cheating the Exisemen

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