I finally watched the adequate (in that they could be post-processed into English, and were terribly mistimed over the ED) subs for the last episode; which really added nothing to what had gone before.
The last episode seemed really like a filler, rather than a happily-ever-after; on an optimistic reading, it could set up a second season. Mr Forty Eyebrows makes no appearance, but we do get a "what they are doing now?" for everyone else; and a brief appearance of another character from the original material, Yoshio Kobayashi, who will eventually become Akechi's adopted son, and leader of the Detective Boys.
Oh, yes. And Engrish. Just to show that they are in England.