Hello @Andrew_Seddon , I am sorry for your inconvenience; the BBC MP3 streams are being discontinued by the BBC and have been removed from Roon accordingly, see
Your QNAP should be able to play aac streams - the ffmpeg used may need to be updated; there are a number of threads about this, for example
However, in the meantime, I can temporarily restore the MP3 file for the BBC station you are missing if you tell me which one it is.