Camphill, 1938 or 1939
The first film of the gliders was almost certainly taken at Camphill, the Derbyshire and Lancashire Gliding Club at Great Hucklow, and probably the crowd scenes are the National Competitions in 1938 or 1939.
The hangar at the very start of the clip is still there. Some of the walls in the later clips have been removed (I helped !) but the windsock is still in the same position.
The gull winged glider seen climbing on the winch launch was a Kirby Kite which first flew in 1935.
Gliding stopped in August 1939 until 1946 for WW2.
Rob F.