Hi Stewart
I once had a 1938 series 1 with a seat bladder (you can still get spare bladders from Uncle Melvyn) so decided to go that route. Bladders are too big so used a couple of wheel barrow inner tubes - good quality ones, two cycle inner tubes, and two lengths of flexible plastic tubing.
Remove air valves from wheel barrow tubes, clamp on the tubing (about 12" in length. Take the cycle tubes and cut off the valve stems, insert the valve stems in the other end of the tubing and clamp.
Hey presto two simple and quick seat bladders. Wrap them in some rubber matting (there are some sharp edges under there) and insert under the seats, pump up until firm - Simple.
David 2001 4/4 4 seater
