You can add BBC Sounds as a Music Service in your Sonos app. Or if you have iPhone you can Airplay from phone to compatible Sonos speakers. Adding the service gives you greater flexibility on using/listening/controlling. 

Go to Settings/Services and voice/Add a service and select BBC Sounds. 
 

@nik9669a I seem to remember this only works for the UK. Not when you reside in Australia as @grazza72  is according to his profile. I've read you can add BBC Sounds if you temporarily switch the country on you profile to the UK when trying to add BBC Sounds. Or you could Airplay the sounds from the BBC Sounds app to your Sonos devices if they are Airplat capable.

Thank you for your help, yep I'm in Australia at the moment so it unfortunately isn't available. But I'll switch my country to UK and hope it allows me to listen. Thanks again 🤩

@grazza72 Could you report back if this solution really works?

Hi there, it does seem to work for now 

@grazza72 hi There - I switched my address back to the UK but BBC sounds isn’t appearing in the services or able to play through my BBC sounds app, is there something you did differently? Thanks

Hi there, not that I recall. I had to wait a few days though for it to all properly update. (Think it took 3 days) then I had to log out and back in to the app. It's very frustrating that it doesn't just work immediately. Hope that helps

You could try to reset the app: https://support.sonos.com/article/reset-the-sonos-app

Thank you @grazza72 and @106rallye - will try both and see what works :)