Aptamil pepti advice please!!!

[Pleasenomorepeppa]

DD2 7 weeks has just been prescribed Aptamil Pepti.
We've been following the WHO advice for bottle prep & have been making up night feeds, rapidly cooling & storing at the back of the fridge.
I know you can't do this with Hipp Organic formula but was wondering if it would be ok with the Pepti?
Aptamil's advice line says that they don't use WHO guidelines & say they don't advise storing any milk.
Night feeds could potentially get quite fraught if I'm making up feeds from scratch. .

One tip I got from here was to make up the full feed using half the amount of water. Shake well. Make up the rest of the water (measured!) from cold and it will be nearly ready to drink. Because the bacteria you need to heat is in the milk not the water, it doesn't matter how much water you use as long as it's enough to dissolve the milk.

Feel free to correct me if I'm wrong, I've seen this a few times on here and found it to be a massive time saver!