To say LHR expansion only benefits the south east is just wrong. The new runway is as much about giving the regions access to the airport as it is about being an international hub. This is why one of the conditions is the added regional connections.
I can respond to that in less than a million words - how about "Ha,Ha,Ha!"?
What will an expanded LHR give the regions that AMS/DXB (to name but two) doesn't give already? As others have mentioned, there are never any comments from airlines when this point is pushed.