2nd runway from Gastwick can operate from 2019, planned opening date of runway 3 at LHR is 2019/2020 - more or less the same
Sources for both please? I don't know the details of the LGW agreement but I really don't believe it would allow BAA/potential new owner to be busy building a runway and extra infrastructure for several years at LGW while the agreement was still in place prohiting just such expansion. And if it did - why are they not busy campaigning for a second runway at LGW now, instead of pursuing one at STN and making no mention of anything at LGW?
Also not convinced a new runway at LHR would take 12 years to build.
The fact remains it's much more more straightforward to expand LHR from a legality point of view. And also more sensible. LGW is not, at present, quite as congested as LHR, it has a backup runway to move onto when things go pear-shaped, and all signs are that many of its higher yielding airlines would be much happier moving their services up the road to LHR - such as CO recently pulling out of LGW altogether and buying more LHR slots.
For long haul I always use Schipol anyway.
Give T5 a shot, IMO a better airport experience than AMS, and indeed any other major European airport with the possible exception of MAD.
Maybe a better solution would be a taxiway between the 2
Sorry, but this whole Northolt idea, and in particular this suggestion, is just utterly ridiculous! The amount of housing, motorways,etc that you'd tear up to and general disruption caused to create some 5-mile long taxiway between the 2 airports would make LHR's 3rd runway look like nothing! Northolt is an important military airfield with a very short runway and heavily constrained movements due to nearby LHR anyway.
Think about the aircraft taxiing time (and associated waste of fuel) that's going to be involved by adding a third runway to the north of the existing ones.
You're shooting yourself in the foot. One of the key benefits of LHR's 3rd runway would be an enormous reduction in airborne and ground holding time, the benefits of which would far outweight any additional fuel penalties from increased taxiing time - not that I think there would be any. A 3rd runway would probably be accompanied by a 6th terminal to the north of the existing site as well, to serve it.