Surely even the most ardent Brexiteer will recognise that it is much easier to trade with your near neighbour than with somebody on the other side of the world. Apart from the costs of transport and travel there is the matter of which laws the contract will operate under. With the EU there is a legal framework in place for arbitration. I have no doubt that outside the EU we could get a trade deal of some sort eventually, but that can never be as advantageous and trouble-free as what we have now.
Let me it it this way, outside the EU would trading with it be:
a) Cheaper and easier.
b) Much the same as now.
c) More difficult and expensive.
It cannot posssibly be (a), at the very best it might approach (b) in which case why bother leaving?
Now consider the situation regards trading with the rest of the world. In my opinion leaving the EU offers us no advantages in this respect.