Okay, you're right – it's more complex than I implied. Switzerland is a single market participant through bilateral treaties, like Norway and Iceland are throu

Okay, you're right – it's more complex than I implied. Switzerland is a single market participant through bilateral treaties, like Norway and Iceland are through EEA. While they aren't "members" of the single market, I think we'd usually consider those four EFTA countries plus the 28 EU states to make up the "single market", though I accept there is no clear terminology in some ways! Still though, such a relationship is equally not the plan of the current UK government, and customs union membership is not a prerequisite for single market 'membership' as such.