It would seem that Parachute Training begun with very low jump practice. Below from a Japanese article, I don't imagine British training would have been so very different! Interesting!
" In the second stage of training, jumps from tables are begun, with the height gradually increased to 12 feet. Methods of hitting the ground and rolling are mastered, preparatory to undertaking jumps with training parachutes, from platforms 12 to 235 feet in height, which feature the third stage of training. During the second and third stages, much attention is paid to instruction in the proper folding, maintenance, and routine inspection of parachutes. Jumps also are made from model plane fuselages at varying heights. Familiarization flights in planes also are made. Aerial acrobatics after the second flight serve to eliminate trainees prone to airsickness or otherwise physically or temperamentally unfit.
Parachute jumps from towers 350 to 400 feet high feature the fourth stage. The chutes are opened by static lines, and oscillation control and steering by manipulation of the shrouds receive suitable emphasis. Control of the parachute also is taught by dangling, with the trainees suspended from the roof of a hangar.