Sound advice XMicelleX!!! I used to do the same! Boil a whole kettle and let it cool, transfer to the bottles and put them in the fridge and use as needed. Stan would never drink it warmed up so cold or room temp was perfect.
I also had the Tommee tipee bottles, so they had the plastic inserts to separate formula powder from water till you are ready to mix up. Brill for day trips out and about, quick and easy.
Formula wise in the UK we have a few choices but not too many to get too confused with. I have heard the !once you choose a formula you should stick with it" but I started Stan on "Cow and gate" when he was born and switched to "Aptamil" after a couple of weeks with no troubles at all but all babies are different. I still use Aptamil now and he's 26 months old now and doing great.
As far as I know all the formulas that are available are specially formulated to be the best they can for your baby. So aside from being milk or soya based, Which is good to know if you have a baby that is lactose intolerant or not, they are all pretty good here in the UK.
Don't worry you will make the right choices for you and your lovely bubby even if it takes a while to decide which one to use!