Just a guess, but do you have to tell sonos where to get bbc radio stations from, ie play bbc radio one from bbc sounds, otherwise it could default to tunein and bbc stations are no longer on there.

Also your sonos account needs to show your country as UK for bbc

Thanks for the reply. Although I've tried just about every permutation of how to ask sonos to play a bbc radio station, I hadn't actually tried yours! But, sadly it still answers with "we're having issues connecting with your music provider". Yes, my Sonos account shows UK. Since posting the question I've tried all the possible fixes I found online..turning things off and back on, reinstalling Sonos app, and BBC app, checking my router's up to date..etc etc.. No joy! It’s going back tomorrow!

I've now found where to set my location on the Sonos app (thought I already had, but obviously not!) so the weather forecast is now available. Also on the Sonos Voice Control settings it asks to set a default service...and guess what...BBC Sounds is greyed out and marked as "Not compatible" . The BBC says I can use Sounds on my Sonos speaker, but Sonos app says NO! I'm not a happy bunny 🤨

Have you called Sonos Support directly to discuss it?

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

No, that was to have been my next move...but I've now discovered I can do all I want, including get BBC sounds on voice control, through Alexa..yay! And, even better, she has a much nicer voice than the booming American Sonos chap! But thanks for replying.