"But the key point is that the UK is a massive importer (and net importer) of EU goods. We will in fact be the EU's largest export customer. Bar none. This is undesirable from a balance-of-payments point of view, but it gives us enormous negotiating clout."
One of the greatest fallacies in all of economics is that buying more from one customer than he buys from you is a bad thing; i.e., a balance of payments/trade deficit. Unfortunately, you commit this error in your recent email blast, copied above. What are the EU countries to do with all those pounds that they accept in payment for vendible goods? They will buy something in Britain, maybe even British national debt. If they let the pounds stack up in their central banks as foreign reserves, all they have done is present a gift to the British people, similar to a merchant never cashing your check.
Warmest regards from an friend in the US,