Mine have always had a singlet, and growsuit, wrapped up tight, in a bunny rug, with one blanket over the top ( summer babies), then when they wriggled out of the bunny rug,( about 4 months) I'd use a sleeping bag, and if really cold, a jumper over the growsuit, and under the sleeping bag, then a blanket over the top.
At 19 months she wears a singlet growsuit, and one blanket, in this weather.