https://www.eatwell.gov.uk/asksam/agesandstages/childrenandbabies/#A302871
above website is food standards agency
When you start to prepare a feed, it's very important to clean the work surfaces and wash your hands first. You'll also need to sterilise bottles and teats before you use them – follow the manufacturer's instructions on how to use the steriliser.
Remember to follow the formula manufacturer's instructions on how much powder and water to use for each bottle. You should also do the following:
Boil at least 1 litre of fresh tap water and leave it to cool for no more than half an hour.
Put the water in the bottle, followed by the powder.
Test the temperature of the formula milk on the inside of your wrist before giving it to your baby. It should be body temperature, which means it should feel warm. If it feels too hot, cool it by putting the cap over the teat and holding the bottom half of bottle under cold running water.
If there is any made-up formula milk left after a feed, throw it away. You should also throw away any milk that has been at room temperature for more than two hours.
Ideally, you should make up formula milk freshly for each feed just before feeding. This is because using formula milk that has been made up and then stored may increase the chance of your baby becoming ill. If you do need to make up bottles in advance, keep them in the fridge and never store them for more than 24 hours.
says its fine to make up and store in fridge x