I've been collecting Peter Dickinson for years - and have all except a couple of stray early ones. I also managed to collect a couple of serious music books by a different Peter Dickinson as well. Anyway, if you decide you'd like to look at some of the ones you can't find (if you can't find any of them) let me know - like The City of Gold or Annerton Pit. Give me a week to dig them, up though!