I am surprised that this thread has gone dormant for a couple of days. Perhaps everyone has either completed it or given it up as unsatisfactory.
I have still got 9 unsolved clues, and have no idea how to expand the thematic answers. I have tentatively fitted 8 answers into the SE corner, but they don’t seem to help with further progress, though they do suggest an end of a word on the main diagonal.
The hints on this thread are not as helpful as usual. The suggestion of ORATORIO for clue 20 has not been retracted, though my answer is much shorter than that. We have had suggestions of a 9-letter answer to 27 and an 8-letter answer to 23, both needing expansion, yet only one expanded answer should be longer than 8 letters.
Any further hints would be welcome. My unsolved clues are 3, 15, 23, 25, 29, 30, 34, 35 and 36.