You're missing the point.
Dribbles doesn't need to sell his fish to the EU anymore, now he can sell it to China because our waters are SOVERIGN again so we can sink any Chinese trawlers who try to STEAL our fish, which means they will have to PAY us for our fish!
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This is a very good point, because one of the main complaints about the CE mark and EU standards in general when they first became the standard for EU members is that they weren't as strict as the BS mark and British standards we already had.
One would assume if we're bringing our own system in again then at a minimum it would be as strict as the EU one, which means any goods that don't meet standards for export to the EU won't meet standards for sale in the UK either, so what is our plan here? To produce Chinese grade tat and try to sell it to Africa cheaper than China can? lol
There is actually something of a historical precedent for this, back when the EU banned plasma TVs it effectively killed them off globally because with the planets largest market for technology now closed to them manufacturers opted to simply cease development and focus on LCD instead of having a separate development/production line for non-EU markets.