Snug Time are great bags hon You may find 1.5 TOG a bit cool for winter though so see how you go. The clothing guide with Grobags (google it - Grobags what to wear) is the best and most 'accurate' IMO however their guides are for sleeveless bags. Still good as a reference point.

We use a 2.5 now with DDs room around 18. A bag with sleeves would only need pjs and a singlet I'd say. As our bags are sleeveless, we use spencers or long sleeved onesies under pjs