At last I can jump for joy! I have the final solution. Although I did not find it by my unaided efforts, I can admire the amazing grid. Stupendous!
If I could ever achieve a grid like this I would think how it might be possible to make it available to the highest number of solvers. Make the clues fairly easy and make the preamble intelligible and helpful! Instead the setter and editor have gone for clues and preamble fit to turn away potential Listener-lovers for life! Not, to my mind, the most suitable Christmas present!
Still, a happy Christmas to all and thanks to Norah and the regular posters who do so much to help us to enjoy the Listener.