There is a big gap in your logic. In your example the country outside the EU is exporting blow up sheep ( ) to countries inside the EU. After we leave the EU it will derive no benefit from exporting them to us for onward export to the UK. Why would this imaginary country want to strike a deal with us? And even if it did what is in it for us? We would have to pay EU tariffs on any blow sheep we exported to the EU and pay shipping costs.
C-. Must try harder.
C-? How dare you. I've never received less than an A in my life.
Why would we export the blow up sheep to the EU, there are plenty of blow up sheep lovers in the UK.