You would have to buy an Airplay 2 compatible Sonos speaker. Your profile lists the Play:1 and the Play:5 gen 1, neither of which is Airplay 2 compatible. 

Thank you, John, I did suspect that, so if I had just one generation 2 Sonos all would be able to play BBC sounds by streaming through the new one?

Yes you could group the new one with your other speakers.  I have had another thought though.  You could play BBC Sounds on your phone and send it to your Play:5 line in.  You could do that with a cable or you could get a fairly cheap Bluetooth receiver and put it in the line-in.  A line-in source can be played to any speaker in your system.

Thanks John I may have a go at that as I tend to listen to the Paly 5 most of the time and the phone is nearby, thank you for your help.