Thank you all for your helpful hints. I now have it all, though I see no ambiguity in the unclued answers. i have been surprised at how unfamiliar with Playfair many people are. Shows my age, I suppose. Ximenes often set Playfair puzzles in his Observer series. I haven't done Azed for years so I don't know if he continues with the occasional Playfair. This puzzle was certainly a sensational variation on the genre. At first sight it seemed totally impossible, since we're used to having answers en clair to compare with coded forms. But once one realised the vital importance of 23 and 41 across light gradually dawned.