I agree with both of you re; looking vaguely SSW from T3. I looked at a few more photos on various forums and it seems to make sense. I always come over a bit nostalgic when I see these photos and have 'what-if?' moments!
What-if I was around to see all of the early central layout and the original runways patten in operation?
What strikes me with these early photos of Heathrow/LAP was the enormous amount of space they had for what were relatively small aircraft and a small number of movements. What foresight!