I am chuffed for you mate, something I discovered tonight while performing more testing.
If the play gets interrupted either be it by a telephone call or the radio kicks in, you need to start up the Spotify App again and press play or else that empty track you loaded will just play.
I guess my method is more a work-around rather than a fix. Who knows an update might come out for B&M that allows compatibility. However for me its a small price to pay, im chuffed I don't need the B&M adapter also so a little saving
