I'm considering the perfect prep for my 2m old DD, but I read some really bad reviews on amazon about it breaking down and reading further into the product, it doesn't actually use cool boiled water does it? Just filtered tap water?
I used formula with DD1 and like pp i made up 6 bottles with boiled water in the morning and used the tommee tippee formula cups, which I added to room temp water throughout the day 
When I switched to formula last week I followed the instructions to a T after reading that the hot water is needed to kill the bacteria, but its such a faff
So I devised my own little method.. When she was ready for a feed i'd fill the previously boiled (now cool) kettle water to fill the bottle 5ozs. I'd then boil the kettle, and fill the bottle lid with boiling water, add 6 scoops of powder, swirl a bit while carefully not spilling any and add the now sterile powder to the bottle, shake and serve. The bottle was pretty much room temp/ luke warm.
But... I'd gone from the freedom of being able to BF out and about whenever she needed, not having to plan anything to wondering how the F we were going to be able to leave the house.
So after reading the perfect prep reviews, i now add 2ozs of hot water to bottle, six scoops, then add 4ozs of tap water.
I've read the WHO guidelines mentioned up post and i'm not sure which is safer, using hot water for powder mixed with cold tap water (what nasties are in tap water?!) or using cooled boiled water for the powder?
Hmmm
very confusing. Btw, DD1s formula was never made with hot water and she was never sick, but obviously you always want to minimise risk. I realise this might read that i'm trying to choose between the lesser of two evils and should just follow the bloody instructions but its a hard and lengthy process to be doing at 4am with a screaming baby.