I believe Apple will be using or supporting three different streaming radio providers with their new Radio feature. As discussed here the leading one is TuneIn from which the BBC have at least for the moment pulled their radio stations from.
However supposedly Apple will also be using iHeartRadio and Radio.com
Radio.com is unfortunately a complete non starter as they do not support connections from Europe at all, iHeartRadio might be a possibility and seems to have at least some BBC stations on it e.g. BBC Radio 4.
I have not tried iHeartRadio since their website seems horrifically broken as it does not work in Chrome or Safari or Firefox on a Mac or iOS - it does not even display content properly including their presumed home page, nor does they search function work either. They like the others do also have an app which I have not tried.
However supposedly Apple will also be using iHeartRadio and Radio.com
Radio.com is unfortunately a complete non starter as they do not support connections from Europe at all, iHeartRadio might be a possibility and seems to have at least some BBC stations on it e.g. BBC Radio 4.
I have not tried iHeartRadio since their website seems horrifically broken as it does not work in Chrome or Safari or Firefox on a Mac or iOS - it does not even display content properly including their presumed home page, nor does they search function work either. They like the others do also have an app which I have not tried.