I also had a problem with 22Dn. A search in Bradford's using the first word of the clue as the headword gave me the solution, and helped me get the second word of 27AC.
Having completed the puzzle, I'm left with a tiny nagging doubt over the second writer. I agree that their names comprise 24 letters in all (14 & 10), but can any fellow sovers confirm that the 20th letter (e or s from 29AC) is the middle initial of the second author (5,1,4)?