for anyone who wants to see old maps, I have found an interesting site at :
www.ponies.me.uk
This is a very clever site where someone has scanned in OS maps from the 1920/30/40s and correctly positioned them. You can zoom in to nearly anywhere in the country.
The clever bit is the "Transparency Slider" at the bottom via which you can overlay the current road layout.
The Heathrow area does show "Heathrow Aerodrome", but not much else !!
Try it.