I appreciate a good discussion, but please stop inventing things and blissfully ignoring reality. Pre-EC we were a part of EFTA, a group of European trading countries. In the intervening years, ALL of those countries are now either in the EU or have complex trade deals tying them to the EU. The situation we had "before" ceased to exist. And just in case you want dig up India and China, our empire collapsed a good while ago, with Hong Kong being the last bit to drift away.
The biggest part (like nearly all of it) of the UK national "profit" is in the invisibles i.e. insurance, currency trading, stock market, etc. In the last 40 years this has done very well, mainly using the UKs expertise and traditional links with the outside world and acting as a gateway (2-way) to the EU. The handle to that particular door is about to fall off.
OK, you voted to leave. Accepted. But if the vote had been "remain" or "leave and create national poverty", what would the vote have been?
So leave, but make sure you have you ducks-in-a-row before you do. Let the Government and Parliament work through this and reach a compromise or process to get what's needed. Of course they could mess it up, but then your no worse off anyway.