Fresh produce will be affected. no trade agreements, it will go through the roof.
I was reading a piece on Greek lemon growers, the EU subsidises them so lemons cost eg 4p each. Albania, next door, also has lemons but no subsidy, so their lemons cost eg 28p each. No one will buy Albanias lemons, because Greek lemons are subsidised so it remains a dirt poor country, becuse of the lemon monoply.
So Greece wont sell us lemons because we arent in the club any more, we'll have to get some Albanian ones at a gazillion times the price. Notwithstanding the Albanian ones wont be grown with EU regulated fertilisers etc.
As they say you get what you vote for.