How to prepare Formula bottles

I am from France and I was surprised to see that on any formula user guides, the use of a kettle was recommended. Boiling the water and letting it cool for 30 minutes doesn’t sound like time saving when you have a very hungry baby on your hands 😅 In France we simply mix the formula with bottled water and warm the bottle if necessary. Is everyone following users instructions in the uk? If so how do you prepare bottles when you’re on the go 🤔? Thank you ☺️