There are people seriously affected by airplane noise. I am not so sure that people in Richmond and Hounslow are. I worked for years in Hounslow and wasn't bothered. A best friend lived in Richmond. I never noticed the noise when I visited her. Actually, I noticed how nice Richmond was, much nicer than I could ever afford. I wonder why your average semi in Richmond is over a million pounds if they are blighted by pollution and noise?
They aren't. They are convenient to the airport but not compromised by it. There are a group of residents blighted by living very close to the airport, but the net is not nearly so wide as you claim.
Also, Heathrow is not in the middle of a city as some have claimed. It is on the suburban edge of a city. It is nearly 20 miles as the crow flies from Charing Cross (the traditional centre of London.)
If we wish to remain part of the world economy and have jobs and growth, we must maintain our infrastructure. Airport capacity is part of that. Heathrow is best placed to serve the population as it is actually distributed throughout the UK.
Of course there will be Nimbyism, special pleading, and special interests. For me, the only debate should be where to draw the line for compensation and how much to compensate. Some people are truly and disproportionately affected, but fatuous arguments should be disregarded!