For those who like to service their own Hornby-Dublo model trains a book on the subject is in preparation. Still being written it aims to be the definitive reference on the subject. Over 8 years has been spent on its inception and still a work in progress, however very nearing completion.
20/07/19 The current status is I am looking for a publisher. Also below is an example of the quality of artwork in the book, all done in Adobe products. Another point about the book, there are now 120 service diagrams, including Wrenn and Acho. Will add more details soon.