2.5m capacity sounds a reasonable max permitted level at the present time.
The SEN Director is in print previously with a total of 15m so even to 10m (which is todays story) as a percentage it is huge growth leap which in todays climate (bit of a pun) is going to be a very tough proposition to negotiate it would appear.
LHR RW3 is almost certainly not going to happen.
Bristol Airport is up against it now with it`s proposals for expansion.
HS2 is almost certainly not going to happen.
STN would not have won it`s own permissions if the new Council had been in place.