Very interested in your comments re The Clocks. I re-read this novel about two years ago not having looked at it for many years. I also was left with a vague feeling of untied loose ends and unanswered questions (so untypical of the great lady.)
You have now inspired me to read the book again and I will specifically watch out for the points you mention. When I have done so, I will post a book review on the Agatha Christie website and hopefully be able to make more sense of the denouement, but I have to say this is not one of my favourite Agatha Christies.