Nick,
Personally, I don't know enough of the issue to take a view. BUT - I don't think a C2 change substantially affects the amount that Defence as a whole is paying for the capability does it?
Bringing Harrier back would have a massive impact on the need to find further savings. Too many Service personnel assume that footing the bill is something for the civvies to worry about.
"You want me on that wall. You need me on that wall...."