Auntie has added radio programmes to the iPhone version of the iPlayer today, so my downloader now supports them too. They are nothing more than plain old MP3 files.
You can get the new versions (0.1.12/1.8) on the project page.
Normally, BBC changes mean that I have to spend a bit of time
working around them. In this case, however, it just worked out of
the box. That was a pleasant change! All that I did was to change
the file extension to
.mp3 for radio programmes to be
a bit more helpful.