I can remember before we joined the EU (then known as the Common Market) when we had good trade relations worldwide, particularly with the counties in the British Commonwealth.
We also had a manufacturing industry, and a solid lead technologically on most of the places we traded with, as well as historic limitations on their capacity to trade in other places. That was more than my entire lifetime ago, it's a different world now.
We lost all this when we joined, because of the exhorbitant tarrifs imposed by the EU for dealings outside Europe.
The tarriffs didn't change significantly, what changed was that we were no longer paying those tarriffs to trade with other places in Europe. Stuff from outside didn't get considerably more expensive, stuff from inside Europe got considerably cheaper. That's one of the key problems with leaving with no deal - we won't have a deal with anywhere else, either, so suddenly we'll be paying those tarriffs whereever we choose to trade with.
We also lost most of our fishing rights from the 50 mile coastal zone.
We negotiated those fishing right agreements outside of the European Community in the late 1960's - entering the EU meant that the EC countries could negotiate as a block with the likes of Norway and Iceland, and actually secure a marginally better deal. If we drop out without a deal, we'll revert to the prior agreement which will see us lose access, overall.
There is a whole world outside Europe The EU is just a dreadful self centred cartel which restricts free trade in order to give unearned profit to its central body in Brussels. When it finally collapses it will be better for all.
There is a world outside Europe - in general it is either significantly poorer and further away, or significantly richer and even further away, neither of which puts us in a strong position to get good trade links out of it.
The EU is no more nor less self-centred than, say, the US, China or any of the emerging economies - we are part (for the moment) of that EU self-interest, and we benefit from it.
O.