You need to stop thinking that 'the EU' receives custom from us. The EU is not one institution. We do not ship to 'The EU'. We do not order from 'The EU'. This is not how it works. Please understand this.
This is how it works.
The EU is made up of countries A, B, C, D, E and F.
We do business with countries A, C and F. We do no business with B, D and E.
Countries A, C and F are gutted that we left. Countries B, D and E are unaffected.
This is how it works. The EU cannot say shit about the business they lose. They lost no business at all. Countries A, C and F lost business. Countries A, C and F would love to agree a trade deal with us to replace that business (about 10% of their yearly exports) but all the rest of the countries in the EU don't care. They get nothing from us. They lose nothing from us. But here's the kicker, they still have a vote in whether our trade deal goes through.
So you need to stop saying that 'the EU' loses a tonne of business from us. No it doesn't. A few countries in the EU lose business with us, the rest lose shit.
Now when it comes to negotiating a trade deal, every country has to vote yes. We go to the EU and we say 'look guys, we need to replace 45% of our exports. Please help us out'. Countries B, D and E say 'what's in it for us? We don't care. We haven't lost anything by you leaving.' This notion that 'the EU' will be crippled by us leaving just isn't true. First of all a lot of them don't even trade with us, and secondly the amount that the ones who do actually trade with us contribute, is very small because the huge amount you think we import from the EU is actually much smaller amounts split between a lot of countries. It does not matter if France are distraught that they lost a tonne of business from us. They need to convince 26 other countries to vote yes to a deal that hasn't affected them. This is where we are forced to agree to things we don't want, because we have to replace a lot more than they lost, and we need to give an incentive to the countries we don't currently trade with.