The aircraft are Tiger Moths, a Harvard, an Oxford or Ensign and a Tutor. This would suggest the photo shows Upavon between August 1935 when the Central Flying School returned to Upavon and stayed there until April 1942. During this crucial period, the CFSs primary role was to train and supply flight instructors to the now increasing number of military flying schools
There appears to be a signal square but with a light background not the usual black and the markings look unconventional. There is a small observation point on the corner of a hangar just left of centre. The buildings by the square are apparently the watch office and are surrounded by a new sandbag enclosure and the camouflage on the hangars looks new so looks like it may be 1938 at the time of the Munich crisis. The grass in front of the hangar seems to have been planted with small trees and the low buildings along the hangar front have a simulated wood painted on them. The towed bowsers appear to be standard Brockhurst bowsers, used by the RAF and presumably the Fleet Air Arm in large numbers.
another photo from Barry Davidson showing what appears to be an elevated watch room on the hangars. Swordfish LS326/5A from the RNHF.