Para jumping at Christchurch 1949/50 ish?

I have just been sent a couple of photos of a barrage balloon at Christchurch
being used for parachute jumping.I had completely forgotten this, which
happened somewhere in the late 40s/early 50s when I was 9 or 10 .We could see
this going on from our garden.I think maybe it was only for one or two summers.

So what I need to establish is exactly when this went on, who was the
organising body (possibly the 89GS?) and anything else anyone can tell me.

MTIA