Like others I found this a pleasing and reasonably quick solve. I wasn't aware of the theme, but that didn't hold me up too long. I could go to be all happy and content if I could solve 15D - the only thing still missing. C has 3 words which fit the checking letters, but none of them makes any sense, even with a very loose understanding of any words which might be the definition. So I've concluded that it must be a proper name. Am I right?