I've thought its Kevin Philips as well. There is a website that is giving reasons why it isn't certain Footballers from the clues in the book like having two daughters etc...
Having said that, I wouldn't be surprised if it is a few people.
I seem to remember some Hungarian website (possibly another obscure nation) revealed Dave Kitson to be him and were forced to take down the article by Sheffield United.
SO we can confirm that it is Dave Kitson.....or Kevin Phillips...........or Danny Mills.................................or Danny Murphy................................................................or Joey Barton.