Man you should read the book... if you think he went on about Phil Collins a fair bit in the film, there is about 2 chapters of him purely talking about Phil in the book !

I dont know what was real and not in the film, the only evidence that he was actually imaginng things was given away in the "Feed me a kitty" bit at the cash machine.

I am half way through the book so maybe will have some more answers for you soon =]