Prior to 617 being transferred in from Hendon, 613 VGS from Halton operated periodic detachments there and on one of these, I got my Air Cadet Soaring Certificate which gave me a BGA 'C' Certificate in Sedburgh VX275.
Those trees in the left background of your photo align the edge of a taxiway which is the bit of tarmac we were allocated to use on our first detachment, with myself (front seat) and Robin Miller (back seat) doing first launch in a Mk3.
Open House.