There isn't a single country in the world now, who aren't part of a trading club. The last one was Mauritania who is now in the African club.
For some strange reason the UK wants to get out and stand alone.
And therein lies the problem .... the EU is far more than a trading union - the union we voted to join. How many of those other trading unions have a parliament, a flag, an anthem, a council, a foreign minister, courts, a currency ? All the mechanisums of state. Turn the EU back to a purely trading union like all the others and we wouldn't have the current mess.