The Rural Life Centre, Tilford, Surrey holds records of an agricultural machinery supplier (J.Gibbs, of Bedfont, Middx) whose firm was situated just outside the airfield perimeter.
Included in the collection is a high definition aerial photo of Heathrow taken, in my estimation, in the late '50s/early '60s.
The photo was on public view until about a year ago, when the display was re-organised.
I'm sure that the photo is still available for viewing...phone Mr. Chris Shepheard, (Curator) on 01252-795571 if you are keen to see it.
Chris is an aviation buff, and will probably remember when we organised a school trip to Heathrow in a Bedford SB, with a guided tour "airside" as part of the package!