When we lived in Melbourne DH and j lived in a tiny place in Carlton while we renovated. Our bedroom was like a freezer but DD1's room was always heated at the exact same temperature. I found a heater essential to stop early morning waking.
But I'm talking about 430am. Anything past 5 is a sleep in in this house until the kids get to around 2 and then they start sleeping in. Now I've got older girls I find I have to wake them on school days.