The main problem with that is that our surplus with the rest of the World is dependent on our EU. membership. As members we have preferential conditions in 50 non EU. markets, which would all need to be renegotiated in the event of withdrawal from the EU. A hard Brexit does not only damage our trading relationship to the EU. but to the rest of the World - all those trade agreements, which we have as members, would have to be renegotiated.
But in the interim, we trade on WTO terms, so trade goes on. And we can fix the tariffs, so long as we apply them consistently across all countries we trade with
They really are a poor lot. Even at Parliment yesterday Corbyn looked weaker with every point.