Just checked this out and to my surprise I was able to get a very clear, albeit weak, signal from Caroline on 648, indoors ,on my restored Vidor 'My Lady Margaret' valve portable in East Herts
I'll check it out later, outside, away from the house and all of the background interference that I get there.....Incidently, while initially searching, I found a similar signal from 'Smooth Radio', on 603, from Kent.......