The thing that gets consistently ignored by those yammering on about how being in a customer union with the EU gets in the way of getting trade deals with other countries in farflung parts of the world is that, when it comes to getting favourable trade deals, the UK on its own is in a far weaker position that the EU. It just hasn't got the clout. Much of the time it will be about knuckling down and accepting what is offered, however bad.

This is referred to as "regaining sovereignty and independence."