I BFed for 10 weeks (very successfully, I've got a proper little chunker of a baby who pretty much doubled his birthweight in those 10 weeks), but then I nearly lost my mind from the hassle of it all so switched over to FF. BFing or FFing is such a personal choice, that I think all reasons for making the decision (either way) are perfectly valid. (As long as they aren't based on crap information).
As far as making the milk up - follow the instructions on the side of the tin, they're there for safety reasons. (Only thing I would say is rather than leave the water for half an hour to cool to 70C in the kettle, pour it into the bottles and leave for 5 minutes before adding the powder, it cools to 70C much quicker in the bottles). For overnight I make up feeds in advance, fast cool them, then heat them up in a bowl of boiling water. The WHO website says its OK to make up in advance as long as they are made properly to begin with and cooled and stored properly. For out and about you can get some really good thermos flasks that keep the water up to temperature for ages, or you can use the little ready made cartons.
I FF roughly on demand - DS wants feeding at approximately the same times each day, but sometimes he's more hungry than others and I wont make him wait until his next feed if hes hungry. Use the guideline amounts on the tin as just that; a guide. You baby may need slightly more or less, but as long as they are having plenty of wet and dirty nappies, and gaining weight nicely, and generally seem content, I wouldn't worry.
Different baby formulas are all much the same (they have to be), but you might find one might agree with your babies tummy better than another, so it might take a bit of experimenting with different brands, or even the comfort milk if she seems like she's very windy or constipated.
Your GP might be bale to give to advice too, if you're finding the HV isn't. (I always feel a bit sorry fo HV when they get picked on for not giving advice on FF, I get the feeling they have very strict guideline on what they can and cant say to mothers. Saying that, mine is lovely so maybe I'm a bit biased!)
Speaking of FF on demand, DS is now squawking for food and trying to eat his sleep suit, so I guess I should get off the internet and feed him. Sigh. 