At first I too thought there might be too many possibilities in the endgame, but I got them all by listing out the possible changes to crossing entries. Perhaps it helped that I'm a member of Chalicea's club, but not too much!
Without meaning to give too much away, if I add up the numbers of the 4 thematics and add the sum of the numbers of the result, I get 16. However, I am desperately in need of a nudge for 1d and 22d.
I usually find the end game the most difficult part of The Listener puzzles. I found this quite accessible, perhaps because the phrase in one of the thematics came up in another puzzle some time ago (Possibly not a Listener). Liked the theme.