I always feel that people should clarify the "Heathrow is in the wrong place" argument as well.
It's only in the wrong place in terms of approaches flying over the centre of London, which adversely affects a large amount of the populace with noise and is inherently dangerous if there were to be an 'incident'.
However, in terms of accessibility it's pretty much spot on, having our nation's only hub airport readily accessible by a huge number of the general population. The road access could certainly be improved, but if the rail infrastructure is improved (which is it being with Crossrail and the direct mainline access from Reading) then that wouldn't be so much of an issue. In addition, with an extra couple of runways the short haul connectivity to the regions will become much better.
In an ideal world I suppose Heathrow would probably be repositioned something like 5 - 10 miles due West of where it is now, something which the Dr Tim Leunig Policy Exchange proposal certainly tries to make an effort at (although 2.7km falls somewhere short...!)