nearly there - tho without being able to parse several - but have no idea about 9a, 15d or 24d (for which I have r_c_). If 23d is what I think it is, I don't understand the grtng bit ... and I know who went to St Cstrds but can't fit him into my presumed answer.
I have all except 9a, 18a and 29a - am completely stuck on those three. In 23d the first bit is another word for grtng (that I wasn't aware of) and the whole word could mean a small one of them (but doesn't). For 18d you have to think of what St Cstrds is (and spell it in the 'correct' way!) R_C_ is correct for 24D.
yes, I was sure that was what 23d was but, like you, unaware of that meaning of the first 4 letters. 18 I think is a 9-letter word, definition
b_ld. Can't get 9,15 or 29 -- leaving it till tomorrow.
You have all advanced further than I have, but I do have 9a, Prospero, though I can't parse the middle two letters. The definition is the first two "words". I am also throwing in the towel for the night.