Was this really a book I read or am I going mad??

Classic holiday read- guy in early 30s who runs a business mending slot machines and is about to get married to his girlfriend who coincidentally cannot have a baby. One morning an old one night stand turns up on his doorstep, I forms him he is a dad and gradually introduces him to his son Phoenix. They bond, fiancé finds out guy is seeing ex and gets mega upset, thinks he's having an affair but then finds out truth and everything is ok... And a couple of things after that.

Tonight I went on to BBC iplayer and started watching the film 'having you' and this is the movie of the book!! But Wikipedia says the film was both written and directed by the same guy. I am so convinced I have read the book and that I have never seen the film before... So much so that I have been surprised by some of the set choices but it is definitely the same story, I have only watched 10 mins or so but have already been introduced to some of the characters, Barry the girl's best friend's boyfriend is perfectly cast but the best friend is a bit washy washy and the acting of the conversations feels a bit false.

Anyone know the film I am talking about and hopefully you know the book I am referring to as well??