as a good proportion of people flying from "thiefrow" are not local, why not build/extend a regional airport?
it would cut down on the amount of traffic to the bloody airport,
Humberside airport lands and takes off over farmland or the sea, and its next to the M180,
norwich has an internation airpost but no decent roads to it. several billion could build a nice motorway too.
Neither Humberside nor Norwich justify the investment - they're too far from the passengers, and are frankly pi55holes in aviation terms. The international airlines already have the option of flying into many of them, but chose not to. There have been scheduled services from Bristol to Newark in the recent past, but passenger numbers simply didn't support it. People would rather travel 2hrs to Heathrow to take advantage of the cheaper prices that come from the competition of multiple airlines.
Any new runways need to be within 1hr of London, and 2hrs of a large proportion of the rest of the UK population. That really means it has to be west or north west of London - in prime Tory commuter green belt. If we were starting from scratch, Heathrow should probably be 'moved' to somewhere half way between London and Oxford, but it'll never happen.
For long haul wide body airliners you need a minimum of 10000ft runway(s) and 12000ft+ is better. There are currently only six 10K+ (civil) runways in England - two at Heathrow, one each at Gatters and Stanners, and two at Manchester. Heathrow needs two new runways - one 12K+ although the other could be shorter (say 8K), Gatwick needs another 12K+, and if Stansted want's one then Ok - but it's not my favourite site.