Knowing the value of my Samsung tablet, I decided to investigate appropriate writing apps. Firstly, there aren't that many or, maybe I should say, there aren't that many good ones. My tablet came with the excellent S-Note, which allows me to handwrite, type, draw, and import pictures, pdfs and charts. It's hard to find anything that offers more. But what I needed was a way to move my ideas around which, whilst not impossible, is not straightforward with S-Note.
I eventually uncovered a rather nifty app that allows you to create index cards, in different colours if you choose, that you can move and swap about however you please. I think this might be the answer. I've begun by noting on separate cards scenes that must feature in the book. Once I have them all, or at least a good portion, I can begin ordering them. After that it's just the simple matter of rewriting the book to suit. (Cue slightly disturbing hysterical laughter.)