I was muttering and griping at this, but then realised that the problem didn't lie with the puzzle - I was just being dense.
Hadn't looked for a theme, but now that I've been guided (Thank you, Jono), I'm feeling well disposed towards it all. The only downside is that I am thinking of Paul Young's cover version.
I would have preferred a different spelling for 24d, but that's a minor quibble.