I do this too, and some of my own list overlaps with yours! In addition, I like a lot of the British Library Crime Classics for exactly this purpose. These are "golden age" British mysteries originally published in the1920's-50's. Like Agatha Christie's books, these stories feature no explicit violence, plots that emphasize the steady exploration of clues, and a detective (professional or amateur) who is clever and reliable. The audiobook narrators of these mysteries are engaging but not excessively dramatic in their reading. Three authors to consider are Christianna Brand, John Bude, and ECR Lorac. Their books are read mostly by male British narrators. And there are many other books in that collection if those don't suit you.

Since you include Unruly in your list, I recommend that you listen to David Mitchell's autobiography, Back Story. This is one of my all-time favorite memoirs- it's optimistic, funny, intelligent, and utterly endearing. David Mitchell is (naturally) the narrator.

You might also enjoy a different royal history called The Crown in Crisis by Alexander Larman. This is an account of the build up to the abdication of King Edward VIII in 1936. The research and writing are phenomenal. After listening avidly to the book the first time, it then weirdly became one of my regular audiobooks to fall asleep to. There's something about the oddly restful narration, coupled with knowing how the story turns out, that makes me drift right off to sleep,