You should be able to Airplay the BBC app to compatible Sonos players (and group others as required). According to your profile you have suitable devices, in the shape of Play:5/gen2, Playbase and Move.

Thanks Ratty, that was the confirmation I needed, and lo and behold, having now looked at it with fresh eyes, I have been able to achieve exactly what I was trying to do. It turns out I needed to come out of the app, go to my home screen and from there, I was able to pick up the “mini-player” whereby the Airplay symbol was showing. A couple of clicks and BOOM, I was sorted! 

I’m going to plead lockdown insanity in my feeble defence