What have you guys done in this cold winter weather to keep the cot warm while baby is out feeding or being settled?

Please don't reply saying you co-sleep... I know how nice and toasty it is when you all sleep together but it isn't an option...

Yet again I have had baby up for over two hours and when he is finally asleep and I get him back into his cot, it is ice cold and he's woken up. Grr.

I've thought of hot water bottle and heat pack... Anyone have any other ideas?