I have a very cheap ($25) synthetic fiber comforter on my bed that is absolutely the warmest "blanket" I've ever used. It is quite bulky, though, but that is mostly because it's a queen size and I have a full size bed so there's lots of extra.

That said, whatever it is on Jacqui's bed (comforter/duvet, etc) is BRILLIANT! Soft and squishy and just lovely.