I'm glad I wasn't the only one who had BLAB, but the help given has resolved 21 and 28 for me now - many thanks.
I've also worked out how the phrase relating to the final resolution of the end game is represented, and identified the other non-clashing cells. Amazing what a cup of tea can do.
Simond9x, you have three correct letters at 31dn and the answer is not a word but a thematic name - well, loosely thematic, as I don't think that he and his antagonist actually devised either of the two featured thematic puzzles. The clue is a stinker.
The title is still a mystery though.