Along with the MP3 streams, BBC Radio streams are also available in the AAC format. I’ve found out or figured out the URL’s for some stations (a bit of trial and error involved) and I’ll post these after I’ve made a little more progress.
There are two AAC streams available. One is a high quality stream available only to folks in the UK (the rest of the world is blocked). The other lower quality AAC stream is available for folks in the rest of the world.