Your main concern may not be immigration Springing, but in terms of campaign strategy that's what the Leave campaign will focus on. It's an easy votes winner.
The official Vote Leave campaign has not focused on immigration at all. It has lots of perfectly good arguments without the immigration issue. Farage, who is not part of the official campaign is champing at the bit and will do whatever he does because we live in a country where speech is still free and you are free to disagree with him.
I have to say I am also a bit concerned about Remain wheeling out Blair, I could really see it backfiring.
Surely not
I demand more Blair, every day, interspersed with more Obama and some Mandelson, Kinnock and Hessletine.
Is there anyone left in the country who trusts him?
Cherie?
Doesn't mean he's wrong in his instance though...
No, of course not. He's only wrong when he's killing millions of Iraqis in an illegal war, he's right the rest of the time 
When you have the last 4 PMs of the country, 2 Labour and 2 Tories, arguing for the same thing, it does suggest they may be on the something.
Lol! Have you considered that 2 of them were voted out of office by the country , one is thought by many to be a war criminal and the current incumbent is Dodgy Dave, i would say their support is a liability. Classic! 
They are on to something -the big corpa Brussels Gravy train.