That was the same as my baby at first, and I thought he was ready to wake after 30-45 minutes. But she says that babies go into a light sleep at 30-45 minutes which is why they wake up. How easily he goes back to sleep if he awakes from this light sleep all depends on how he is used to being put to sleep. If you always rock him to go to sleep for his naps then he will expect to be picked up and rocked back to sleep from this light sleep that he enters after 45 minutes. If he always falls asleep on the bottle, he will feel like he needs a bottle to go back to sleep. The one thing I didn't listen to in the book (which I now regret) is letting my baby fall to sleep with a dummy in his mouth. Now, when he wakes up, I have to go into his room and put his dummy back into his mouth.
Gina Ford doesn't tell you that you aren't allowed to cuddle your baby before bed, or that he isn't allowed dummys, bottles when he wants, but she says that you should only do these things until your baby is HALF asleep. Once you can see he is getting dopey, put him into bed. So if he falls asleep on the bottle then rearrange his nappy so he wakes up slightly before putting him into bed. Or take his dummy out of his mouth once he is half asleep and settled.
In my opinion, it sounds to me as though your baby is overtired, which probably makes it difficult for him to settle (he fights sleep all the time) and is very grumpy when he wakes. It sounds horrible and is a very last resort, but if you know your baby isn't hungry, has wind, needs a nappy change, needs water due to thirst etc, then you have got to let him cry for 5 minutes, 10 at the very most. It's horrible to listen to and I felt so guilty but it was the only way he would wear himself out and fall to sleep immediately after, making him happier once he has woken because he's had a full sleep. Even the dummy didn't work at this point. After I did this, he soon got into a routine of sleeping more.
Are you giving him enough milk during each feed? Is he falling asleep on the bottle and not having as much as he needs? Have you tried giving him cooled boiled water inbetween each feed if you know he isn't actually hungry? He may just be thirsty.
She says you should put them in a dark room so that the light doesn't wake them once they go into a light sleep after 30-45 minutes. That may be what's happening with your baby. If he hates sleeping in a dark room it may be worth turning the light on in the hallway outside his room instead of having his bedroom light on, and each night shut the door a little bit more so he slowly gets used to having less and less light going into his room each night.
Other than that, he may be going through a growth spurt if it has only been happening for a few days. I'm assuming it's a long term problem though.
Feel free to ask anything else. In the back of her book there is a section on common problems in the first year. I found this really helpful.