I'll humour you for a while.
What are these exports? Goods, services?
What do the EU importers then do with these goods services? Are they sold on, included within other products/services, used under licence, used because there are no other suppliers?
What would the importers do if their supply was cut. Could they cope, what would the business cost be?
Now these are largely rhetorical questions because if there are importers of 48% of our exports, then presumably there are reasons why they are importing from us and nowhere else. Therefore the impact if that were to change (if it even could, think patented goods) then no commercial enterprise wants that. That's basic economic sense. That means it becomes a negotiating issue. A jobs and business issue, a criteria for a negotiated agreement.
That's how negotiations work.
Your inference that just because the UK exports "x"% it has more to lose, is flawed logic. It lacks a basic grasp of economics.