What percentage of the vote was required to join the EU? The EU effectively constitutes a relinquishment of sovereignty, but that's not how it was sold to citizens, they were told that they could leave at any time.
> The United Kingdom consulted its citizens directly only after joining the European Communities: following the British general election of October 1974, the Labour government of Harold Wilson held a referendum to fulfill one of its campaign promises. The non-binding referendum was held on 5 June 1975, some two and half years after the UK's accession. It was the first ever national referendum to be held in the UK, and the "yes" vote won by a landslide 67.23% on a 65% turnout with 66 out of the 68 local counting areas returning majority "yes" votes.
You remember the story the citizens were sold but not the vote requirement seems odd. From a minimum of research, it seems there was no vote to join the EU, which did not exist at the time (1973) of the European Communities project with common currency and the rest. But in 1975 they had a referendum to stay and decided they would with a 67% Yes.
> the EU effectively constitutes a relinquishment of sovereignty
Agreed, it is pooling sovereignty. The UK already does that with a union of England, Scotland, Wales and Northern Ireland. Pooling sovereignty is often regarded as a benefit on the whole.