Be careful of nans as this is what they use in hospital to fatten up small babies it for some reason will make very big rolly polly babys if your baby isnt underweight... I used Karicare you can get these in one use packs a any chemist.
Sorry but that doesn't ring true for me - about making rolly polly babies. My best friend uses Nan and her child certainly isn't rolly polly. You may find some sample packs at the chemists (although I found they were always gone by the time I got there - typical lol). I used Karicare when I first converted my daughter over and she took to it so that's also something to try.