Hi @alip43,
I’m sorry to hear you’re having issues removing Sonos Favourites. I just tried this with my system and I was able to remove Sonos Favourites even after the service was removed. Are you able to try using a different controller, such as another phone or a desktop computer to attempt to remove these playlists?
If you don’t have another device you can use, then reset the Sonos app and attempt to remove the playlists again.
I hope this helps!
@alip43
I can confirm using the Sonos desktop controller helps. 
If you just use mobile devices, a 3rd party controller app probably also will do the job.
Thanks for your replies. When I tried at first it would still be greyed out but if you highlight - and not select (no check in the tickbox) it will let you do it.