There is no need for EBM to be at a specific temperature for safety reasons, it just comes down to baby's preference. My boys would drink it straight out of the fridge and in fact preferred that to waiting for it to be warmed! Room temperature is fine too. To make it as easy as possible, I'd thaw the milk in the fridge so that is ready to be used when your DS wakes up. It will keep for 24 hours in the fridge if it's defrosted in the fridge, whereas EBM thawed outside of the fridge (in warm water) will only last a few hours. You could try straight out of the fridge for ease, or in this colder weather warm it up under the warm tap for a couple of minutes. The quicker and easier the better - especially with a crying, hungry baby and all of you wanting to get back to sleep.