My understanding is that the official stance of encouraging Turkish accession has been used as a carrot dangled in front of the Turkish ... but with no real intention of ever letting them join
Well, that policy has certainly worked well. How many votes have we in Remain lost to "the government is lying about Turkish accession"? News that it's a different sort of lie isn't exactly campaign gold.
so from the British perspective including countries that are not culturally European is a way to steer the EU away from deeper political integration.
Hey guys! Massive uncontrolled immigration from a country entirely inimical to our values is a great way to make it easier for us to negotiate over courgette subsidies in Brussels! Sucks to be you, but never mind! Great for us!
FFS. This is the very definition of an isolated elite making political decisions without consent. Once we've left the EU, we won't have to worry about any sort of integration, nor about Turkish accession, but not in a good way. Turkish accession is never going to happen, at least not in the lifetime of anyone able to vote. Why not say, unambiguously, that the British government will veto any application and have done with it? This is worth the margin of victory, at least.