Loxley,
I see you haven't responded to my post. Maybe because there is no argument against it?
I'll recap for you.
NSL does not need to be fattened up for a sell of, though a cheaper pension scheme does indeed help this.
All NATS has to do (and if Barron wants to run it properly as a business, he would do), is to walk away from loss making contracts when they expire. It would have nothing to do with selling NSL, and everything to do with making it more profitable for NATS as a whole.
It's not a course of action I would support, but its a feasible one.