Peter, you have deliberately misrepresented what I have said.
It is the leave campigners that have raised the issue of Turkey's imminent membership of the EU which could not be further from the truth. There is a leave poster doing the rounds implying wrongly that 70 million Muslim Turks are about to descend on the UK if the UK remains in Europe. The leave campaign has been consistant from the outset in playing on people's fears of immigration and yet if the UK was to leave the EU the streets would not suddenly be cleansed of all immigrants, the jobs they are doing and the houses they occupy would not suddenly be available. There will be no 'getting our country back'.
You said that there are already large communities of Turkish people already living abroad including in the UK.
As Turkey is not part of the EU they have been able to do this through other already existing means that have nothing to do with the EU. My point being that if Turks want to move to the UK there are already ways they can do this. In or out won't make any difference not least because the visa issues being discussed in Europe with Turkey are not about freedom of movement to live and work, just visa free travel for booking holidays in Europe, and this excludes the UK.
I made the point about the UN and NATO merely to highlight the point that if the UK wants to take an isolationist stance then perhaps they should reconsider their membership of those organisations too. The UN in particular and the UN Conventions and Treaties they have signed are in fact what has enabled many Turks to migrate to the UK!