Yep. The balloon was similar to a WW2 barrage balloon, and was in use form 1941 until about the early 1990s. The 'cage', suspended below the envelope, held up to six jumpers plus the dispatcher, and was open to the elements. In the floor was a coffin-shape hatch, a legacy from the 'old days', when dropping from Whitley's, Albermarle's, Halifax and even the Beverley.
The whole contraption ascended to 800 feet, which of course could be slightly less if there was a bit of a breeze pushing the balloon. The wooden 'walls' of the cage were roughly at waist level , so very easy to look over the side as the details on the ground got smaller, and the silence prevailed - apart from a strange 'thump-thump-thump', which one eventually realised was one's heart!
The door, if it could be called that, was an opening in the walls at the front of the cage, 'blocked' by a thin metal rod across the top of the walls, with the upper, horizontal frame holding the anchor point for the static lines. Each jumper was called forward in turn, with the order 'Stand in the door!', at which time the metal rod was un-latched and, with the left foot over the sill, right leg braced, the jumper prepared, hands on the vertical 'door' frames, until the command "Red On!", when the arms snapped down, folding across the chest-mounted reserve 'chute.
At the command "Green on, Go!", the jumper launched out, back straight, feet and knees together, head bent back to check the canopy deploying. Experienced jumpers would exit in their own time, calmly and without commands.
The initial drop was around 100 feet as the parachute deployed - cold, clinical, straight down and fast!
The legs tended to swing up in front, as gravity took over, and the upper body weight bent slightly back, and by the time the canopy was fully deployed, and the parachutist stable, a vertical drop of something like 250 to 300 feet had been completed.
It was quite scary, being so quiet and clinical, with that vertical drop, and there were a number of refusals, both on the basic course, and later, during 'fun' training drops, when the balloon was used as a relatively inexpensive way of maintaining currency in parachuting. I must be slightly 'bent', as I quite enjoyed 'fun' jumps from the balloon !!
Aircraft jumps were much easier, as regards the 'guts' to jump, being noisy, bumpy, and without that cold, clinical, gut wrenching vertical drop, because the slipstream kicked one up the Rs, and the canopy deployed quickly. Plus, one was normally glad to get out of the hot, stuffy, smelly, noisy, bouncing aircraft (especially the 'Herc') and relieve some of the weight of all the equipment carried. Aircraft drops were also done from 800 feet normally, although 'tactical' drops could be from 450 feet - just enough time for the canopy to open, drop equipment and prepare to land. All aircraft drops were potentially more dangerous, due to risk of collision, entanglement - or worse.
As for a balloon breaking free and ending up in Norway, I wouldn't be at all surprised. I'd heard tales of rogue balloons being intercepted by RAF fighters over the sea, and shot down, to prevent hazards to air traffic. There was a 'rip' panel, about a foot square, on the underside of the envelope, with a rip cord running down to the cage, near where the dispatcher stood. In the event of a 'break free', the dispatcher would allow the balloon to ascend, as he unhooked the static lines, and ordered each parachutist to exit the cage, one after the other, as quickly as possible, using their reserve parachutes. He would then pull the rip cord, which (theoretically) detached the panel, allowing the balloon to slowly deflate, before bailing out himself. The balloon would (theoretically) eventually return to earth somewhere, and (hopefully) be recovered.
The balloon was replaced by the Chinook for initial (pre-Herc) jumps, bimbling very slowly forward from the hover, with the same rate of jump as the balloon, that is, individual jumpers, spaced to allow preparation etc.
When I find them, I'll post some pics of the balloon.
And I've just noticed Grant - the pics live up to the name for NZ, 'Land of the Long White Cloud'!