It was taken in the 50/60's...and along what is now the pedestrianized High St!
Heres a better view of where it is, & some other photos showing the whole stretch around Lewes....great photos:
https://www.ghost-trains.com/lewes-photos-and-map-positions.php
You can still follow (on google earth) where the line went from Lewes - along by the nature reserve to the pedestrianized high street area (I believe there are even paving markers on the ground where the trains went out over the road from the depot) through the Malling playing fields to Church...