New siri remote will arrive tomorrow - a fast service from Apple support!
I have just been doing some searching about Siri remote Firmware versions. I neglected to say previously that the remote that doesn't control my B&O TV is the 'newer' version with the white circle around the MENU button. The older (working) remote does not have this circle. I had previously thought that the remotes were identical inside, but have just found the following links that would indicate, not only are they different inside, but they are running different firmware:
Original (first generation) siri remote FW versions: link
Location: Warwickshire, UK
My B&O Icons: