It works like this. After the Second World War. The allies divided those countries formerly our enemy, between them.
Some became communist as they were aligned with the Russians. Some became independent countries and some leaned more toward NATO and 'the west'.
This was done because thinking at the time leaned toward the idea of trade blocks. And the best way to counter a communist nation who could massively produce goods at far cheaper prices than anybody else!
The U.S.A as one block, the Communist countries as another. And so the thinking was Europe would become another.
Each doing business(or not) with each other! And subsequently equalising the balance of trade around the world. So that no single nation could undercut any other with regard to products.
With me so far?
The European Union was formed from the old 'Common Market' idea of the '60's.
The thinking is that if Euro nations band together, they'll counter the 'threat' of over production and cheap imports from 'None E:U states' I.e China; South Korea; Japan;
The U.S. etc.
And if you can create a new currency that runs across all member states, theory is that ANYBODY from ANY E:U country. Can freely live and work ANYWHERE within the E:U.
Weights; measures; pay; taxation etc. will ALL be standardised across ALL member states!
This idea was opposed by Britain when it was first mooted about a 'single European Currency' back in the late '80's.
Because it essentially helps to erode a countries identity!
Since then. Following several economic recessions; slowdowns; Brit.P.M. Thatcher's government selling off EVERY national asset/production company.(Energy. Coal. Gas. Car production. Ship building. Etc.) saying that they were no longer prepared to back them with public money!
Thus: Britain no longer produces competitive products on a mass scale. Germany, France, Italy on the other hand, DO!
So in order to be 'seen' as a member of the E:U club. 70% of all imports(estimated)
come from Europe. Plus the U.K is the fifth largest contributor (financially)
The proposed new version of the E:U is the vision of Angela Merkel(German chancellor) and the French premier Hollande.
But it does not suit Britain as it largely favours the more industrial nations.
There are other issues too!
There are lots of conditions to being in this 'club'. Including following directives from various quangos within the E:U that it's said hinder productivity. Including the Working Time directive and others.