Re: Here be snowflakes...
"Parallel example: New Zealand maintains its own technical standards. But for nearly all purposes, it also accepts Australian standards as valid. Australia, for its part, generally (i.e. across most markets) accepts either US or EU certification as sufficient to allow a product to be sold.
The UK should simply rule that anything legal to be sold in the EU is also legal in the UK. The converse doesn't have to be true, though. If manufacturers decide they don't want to sell to the EU market, I don't see why they should be required to."
This may be fine to begin with. But once you have the power to make your own, separate rules, the temptation to actually do that increases substantially. Add politicians and 'think of the children' and 'security' etc and you may find that the train wreck isn't going to happen instantly but be a slow-moving one. You may fondly hope that they will only replace dumb rules with better ones, but they may just go the other way - Ministry of Silly Walks anyone?