Sorry for the delay.
I gave up in the end and brought a Clip Plus. I now use my Jam for music, which it does very well.
I will say that, when I put music on I left a few podcasts on, too. I use Windows Media Player 11 to synch music and, when I had done, found the podcasts were now arranged in the correct order. It may have been a fluke, or there may have been something in the synching that adds some data to the files or just arranges things on there properly.
I’d drag-drop them to the podcast folder, and they’d present as higgledy piggledy despite all my faffing with tags. I synch things to the Jam using WMP and suddenly they’re in order. It may have been a fluke or coincidence, but it may be something worth trying.
Good luck!