Well that was a slog. I found this tough more because I just don't think I'm on Brockwell's wavelength not because of any fault with the puzzle. But like others 21a did involve some very specific UK GK. Hopefully involving a prison sentence in the not too distant future.
I do like the theme but would not have noticed it but for this forum so thanks all for that.
FOI 6d. LOI 4d. COD 15d I think.