Thanks guys, I think i have come to the conclusion that at least one turbo needs to come off. Like Skip says the studs look very brown and stuck in good with all the heating and cooling etc. I am sure they will not come out without massive effort on each one. And I just don't how on earth you access the bottom bolt on the rear turbo closest to the block!
I can't even feel the nut with my finger let alone get a spanner in there!!