Just checked 9A here in North Herts, 2nd floor flat. It's a slightly stronger signal than Cambridge on 9C. That's on my bathroom window, 2nd floor flat, DAB+ set with stereo speakers using its own aerial.

Means when I tune to Flashback I get it on 9C, when I tune to Caroline I get it on 9A. The 9C signal sometimes fades if you walk in front of it. Am well outside the coverage area for both.