The only figure I will give you is that the latest YouGov poll suggests that 55 per cent of the electorate supports the UK's continued membership of the EU. Right wing extremists who imagine that an EU referendum will be the beginning of the end of immigration are delusional fantasists.
But why wont you offer your own view on numbers ?
Be honest, if you want a wholly unchallenged number of people entering the UK then run with it.
I suspect that any right wing extremists have far greater ambitions than exiting the EU, or is it you just misrepresenting those that have a view differing from you on immigration.