//‘but the markets of such third countries would not be open to our exports since we would be outside the EU’
Buhlshiyte.//
Er…not quite the cattle excrement you suggest.
The Good Professor Bogdanor makes a very important point. Being inside the EU’s Customs Union does not make us party to any trade agreements the EU may conclude. It makes us subject to the Union’s tariff arrangements when it comes to imports but does not necessarily allow us to take advantage of the EU’s trade agreements when it comes to exports. The idea of a Customs Union is to protect it members from external competition by “encouraging” consumers to buy goods from within the union (aka taxing the stuff which comes from outside). In this respect the EU’s CU is particularly perverse. For example, no bananas are produced in the EU so there is no opportunity for consumers to buy EU bananas. But the EU imposes a 10.9% tariff on all banana imports. Why should this be? It has no banana industry to protect and the result is that UK consumers are paying 10.9% extra for their bananas, 80% of which is passed directly to Brussels/Strasbourg. So, Zacs, when you next ask how the EU affects people on a daily basis, you can add this to your list which includes light bulbs and weed killer.
Customs Unions are fine if you are content to sub-contract your trade policies to a foreign third party (who may not have your best interests at heart, especially when it has so many economically diverse members). If you want to conduct your own affairs they are not for you. Quite why the Labour Party is so keen to see the UK shackled to one is a little puzzling. If only trade is being considered (which seems to be the be-all-and-end-all of Brexit discussions) then the single thing the UK must do if it does nothing else is to leave the Customs Union. It’s great if you want to trade solely within the EU but the few advantages it bestows are but nothing compared to the disadvantages for companies who seek to trade on a wider basis.