I use an Australian cotton wadding in the middle of my quilts. This provides a lightweight blanket kind of warmth. My children use them in the Summer as a quilt and in the Winter for additional warmth on top of their quilts.
The thicker 'puffier' style quilts have polyester inside them which I avoid as I prefer to use natural fibres where possible.
I do have a 60% Wool / 40% Polyester I use for Pram Liners and Play Mats which is slightly heavier which can be used in quilts if custom ordered.
I generally find many people like to layer their babies in colder weather, indeed I used to do so:
