It's quite simple to build a system that works. UK retailers are liable for legality, safety etc. You don't just dump another new piece of crap on the shelf. Larger retailers have a formal process of becoming a supplier to them that has your products tested, and random sampling of what's coming in until you have proved yourself enough to be rated trusted supplier. There's a lot more to it than "will it sell?".

Even wholesalers and cash and carry places will normally have systems to ensure what small sellers are getting are safe and legal.

Amazon is the big fat exception as they're busy being "platform" and try to duck their responsibilities with "not our problem".

Nett result is I trust anywhere on the high street, even poundshop and other bottom end chains, more on safety and counterfeits etc than Amazon.