The argument that leaving the Customs Union will lead to a reduction in the UK’s food prices seems to originate in a Policy Exchange think tank paper. But the “evidence” for this is a list of EU WTO tariffs on agricultural products. policyexchange.org.uk/wp-content/upl… Here’s where the UK imports fruit from, the EU (and that includes us) has tariff-negating trade deals with pretty much all these countries (except Brazil).

"Last year, for example, it was well-documented how Spanish orange producers successfully lobbied for an increase in orange tariffs."

I think you mean inaccurately-documented. By yourselves. The EU didn’t increase tariffs fivefold because of Spanish MEPs protests, quite the opposite in fact.