Brendan I’m also stuck on 4d. I have no idea what type of thing 12a might be.
24a made me exclaim out loud that it was “such a clever clue”!
My clue of the day (unless one of the two unsolved clues above usurp it) is the beautifully constructed 29a, which reminds me of Winnie The Pooh, and the concept of this thing is so British and in general a really good idea.
I enjoy reading the posts on this forum and appreciate the hints.