When DS was a little bubba, I had him in a singlet, a fleece onesie and then a 2.5 TOG sleepingbag on him. This kept him warm and toastie for the first 2 months.
Then as it got colder, I had a long sleeve t-shirt under the fleece onesie as well.
I also had an oil column heater that I hooked upto a timer. I would have it switch on at 5am til 7.30am so it was warm when he woke up.
He used to be a terrible tosser and turner and always kicked his blankets off.
We only recently stopped using sleepingbags as he finally has stopped tossing so much. He's now nearly 2.5yo and actually loves to pull up his quilt and get all snuggled up and cozy. Plus when I go to bed, I always check to see if he's still tucked in.
At the moment he does get cold in the morning, so he gets up at 5am and jumps into my bed to have another hour of sleep.
I will be putting the heater in his room this week.