Why oh why BBC, must you continue to use proprietary formats for audio on your website? Please would you switch to an open format such as Ogg / Vorbis without delay.
With an open audio format, anyone can write the software to listen to it, giving your listeners the maximum freedom. Proprietary formats are often opaque and encumbered with patent / copyright restrictions and can tie users in to particular companies.
So come on BBC, unshackle your brilliant content!
I'll let you know their reaction...