I'm amazed there isn't a book/film about his time at Watford. One of the world's biggest pop-star's taking over his hometown club and taking them to 2nd in the top division and to an FA Cup Final, all whilst dealing with his addictions and being gay in a very toxic industry is an incredible story. I know there are books that mention it, but none specifically just about that period as far as i'm aware? Why not!? It's a better story than the Damned United, which is a great film.
Have you not seen Rocket Man which covers Watford FC extensively? By which I mean a rabble of Watford players are briefly seen on screen during some kind of drug-induced dream sequence. What more do we need?