With regards to a new airport in the Thames Estuary, that is just a piece of propaganda whenever someone talks about a new runway at LHR.
Lets get something straight. London is not Dubai. You can not just ship over 200'000 Asians to build the airport 24/7 over 3 years, dirt cheap and with no 'elf 'n' safety' regime. A new airport in a country like the UK would be the most expensive infrastructure project in the Western World, will go well over budget and will probably take the best part of 20 years to build. It is not going to happen.
You will never ever be able to justify that amount of money being spent when the capital already has 4 airports - or is it 5 airports now with "London" Oxford!
Common sense will prevail - i.e Stansted/ Gatwick/ Heathrow will get a new runway, regardless of what Greenpeace think or say. London needs a new runway and adding a runway to an existing airport is by far the cheapest and most sensible option to building a whole new airport.
A new airport will not happen. If environmental groups and/or airport neighbours succeed in stopping a new runway being built, then that is it. There will be no new airport.