You wrote in post #9 ... "12a is entered in the grid as ABE...". I assume you meant that 'ABA' is entered into the grid and the superfluous letter is the 'E'?
Thanks Jim C - yes meant enter "ABA" in the grid with "E" superfluous.
Y is the superfluous letter in 2d - it fits in the conundrum word mysterY
Think I'll save sorting 21a &38d till tomorrow!