Thanks ladies. When I was in the maternity ward the midwives were telling me I shouldn't give any extra feeds. If she really cried, then I could give an extra ounce, but no more. I think having been told that has made my concerns worse, because I'm paranoid she'll be having too much. You made a good point about it not being greed at this age; she must need it if she's crying for it.
I went to see the HV today. They refused to weigh her though, and I have been told in the past it's because mothers would compare their baby's weight to their friends' babies' weights, and get worried their baby is too big or too small, and increase or decrease feeds accordingly when it's not actually necessary. It's annoying though, because that's not what I would do, and I have no other way to weigh her and I wanted to know if she was heavy enough to permanently up her feeds to 6oz. It's irritating if you have a genuine reason for wanting to know, but I guess I will know more when she has her next official weigh in next week.
She didn't even look at LO, or consult her notes, but just told me to give her Infacol (which doesn't do anything, and I'm not sure why she even suggested that TBH; I went there because she was hungry, not because she was colicky) and giver her an extra ounce at every feed. I'm not sure I will automatically give her an extra ounce, but only give it if she doesn't seem full at the end of a 5oz feed.