On my RC
Heated seats come immediately.
The cabin heater control is on immediately but the fans will not spin up until there is heat in the cooling system, usually a couple minutes, when left on Auto. I can force them on by selecting the front screen demist function but obviously just blows cold.
Rear screen and mirror demister/heaters come on immediately and very effective they are too! The rear screen is de-iced by the time I've scrapped the front clear..