Not books, but if you want to follow up on this theme, I highly recommend Foyle's War, which includes at least one episode with a child sent from London to the country (depending on your DS's age -- as I recall, the first episode or so is rather gruesome wrt the murder, but after that, the murder mysteries become almost secondary to the characterization and historical stuff); and Enemy at the Door, a BBC series from the late '70's about the occupation of Guernsey. And a little further afield, not about England, there's a book called "Twenty and Ten" (later abridged and retitled "The Secret Cave") by Claire Hutchet Bishop, about children at a school in Nazi occupied France.
