Thanks Mack.
Got there in the end!
On rechecking the whole grid, I realise that I have three that aren't thoroughly parsed.
7D: I assume I'm looking for a Scottish word for cows (not `coos'!) to remove from a longish word for `preserve'?
1D: The answer is unambiguous, but I can't see how the 4 letters (around the disheartened bit) relate to `cast'.
23A: I know I've removed the correct word. The definition works. But what on earth is the wordplay? (I had something earlier, but that was with the wrong word removed.)