We haven't put the heater on yet (in Adelaide and her room hasn't gone under 19 yet). We will set her room to 20 this year I think. The heatermate will cycle the heater on and off to maintain that temp, last year we used a convection heater but it needs replacing and I think I'll get a panel heater.
DD is in a wondersuit and 3.5tog ergopouch sleeping bag. Also have a 3.5tog plum sleeping bag with arms. Prefer the ergo as the filling is cotton not polyester. The ergo website has a good temp guide with what clothing to wear.
Also get a groegg so you can easily check temp.