We already buy lots of stuff from non EU countries...however, I refuse to buy green beans from Zambia as the carbon footprint is ridiculous.
The big supermarkets have spread the myth that the british housewife/husband demands that all fruits and vegetables are available 355 days a year (and 366 in leap years) but this is just wrong...we used to look forward to the quality produce that appeared in-store at certain times of the year, for example, here in Scotland we eagerly awaited the Ayrshire potatoes, the Clyde Valley tomatoes or Carse of Gowrie raspberries and strawberries etc but now we are proffered all manner of such from Spain and Morocco and many other places well outside the EU...and why would you give M&S £9.99 of your heard-earned for 2 tiny bream farmed in Egypt?
Time we supported our local producers, particularly our fisherman who have had to send all their produce, specifically shellfish, to the continent where they are willing to pay more than we are here in UK.
As always, the market will find its own level...