Very few drive in London but the act of driving (whilst more expensive and not especially quick) is only a small part of the equation, as there really aren't that many places to park in central London, and doing so makes the congestion charge seem like peanuts. If people do have cars, it's either those using it for work or those living (and driving) in zone 2 and beyond. I've lived here over a decade now and haven't had a car the entire time. It's just not necessary and a generally inferior means of transport to cycling.
You can only present so much evidence, but as shown, the pollution from Heathrow is contained in that part of west London, whereas pretty much all of central London has Heathrow-type levels (probably 10x the area of the Heathrow patch), and a good chunk of the Heathrow emissions will be the road traffic around the airport. As it is, you've spent most of this thread denying that air pollution is a problem at all, so you'll have to forgive me for taking you with a pinch of salt Pete.