We actually put half and half in each bottle. It's probably a weird thing to do, but we did it to slowly introduce hungry baby milk in case for some reason it didn't agree with her, but she was happy and started sleeping til 5.30am at 3 weeks then til 7am at 6 weeks. We daren't do anything else now!
tbh I'm not even convinced the hungry baby milk is THAT different, has the same no of calories, just ever so slightly more protein and carbs, if you look at the label. (I'm talking about Cow and Gate, others might differ.)