The 1974-1977 photos were taken before the Imperial War Museum assumed control of RAF Duxford. Before that it was shared by several different organizations, all fighting for ultimate control. The Imperial War Museum's acquisition of Duxford probably was the best thing that happened to the facility.
For photos during Old Warden flying days, see Shuttleworth Veteran Aeroplane Society in the Shows/Open Houses folder. Visited several times during my service in Britain: 1974-1977.
Sadly, the Strathallan Aircraft Collection closed in 1990. There had been a show 4 days before my visit according to my notes. Research shows it was held on Saturday 17 July.Visited on or about 21 July 1976.
Visited in summer 1975.