It's interchange Dave. Having rail links etc is irrelevant, those changing from one flight to another don't want to have to embark on a train journey, manhandling luggage etc when going from one tiring flight to another. They just won't do it and will transfer their business to Schiphol or Frankfurt for their excellent facilities.
I understand the point you make 'flecc' but unless we replicate the kind of facility you mention at an alternative venue, we will continue to hear calls for further Heathrow expansion in exactly the same way as has happened with the M25.
As sure as night follows day, a third runway will bring about the need for a 6th terminal and so it will go on. Flights are then likely to double according to some analyses so we may need to sacrifice even more villages than those at risk currently. This situation is unacceptable when, you may remember, T4 was supposed to be the last expansion that BAA would require at Heathrow. When T5 was mooted, it was almost universally opposed by everyone except the government and BAA at the inquiry all those years ago. The people were ignored.
Now, I know you are a very tolerant fellow but for many people the effect of airport expansion is intolerable. Perhaps even worse is the detrimental, physical and health problems which can be levelled at the more heavily-condensed airspace over Heathrow Heath and the air corridors surrounding it. This is all the more galling when you consider we have the space to extend Stansted into a world-ranking international hub airport, simply by moving a few cows up the road.
I still remember when the main London airport was Croydon aerodrome and when it finally closed due to the expansion of local towns and villages effectively preventing any further development there, Heathrow Heath was selected to become the London airport of the future, relieving Northolt and Blackbushe of the increasing volume of international flights in the south of England.
Unfortunately, the same thinking which was applied in the case of Croydon has not been transferred to Heathrow where politicians seem to have no hesitation in permitting quite possibly the destruction of historically-important villages simply to accommodate more air traffic.
Once again, the people have been ignored and politicians have got their way again. Meanwhile, those same politicians are hell-bent on getting the country some kind of deal from the EU because some want to leave that group of nations. I fear that yet again, the people will be the losers and the rich few will share even greater wealth.
We are committing a national Hari-Kiri thanks to the incompetence and greed of those whose duty it is to represent the views of the people and to ensure the welfare of the nation.
Tom