The difference was pre EU you could choose just to sell your product in the UK so you didnt have to through the rigmarole. The EUs idea of standardisation seems to be to push all the rules together into one regulation .But it was never simple before, but you had to do 4, 5 or more times, each country having its own quirk. A total nightmare and a big expense, multplied by the number if countries you wanted to sell in.
Btw are you confusing EEC and EU?