Having had the sunroof missed off of mine (easy to spot!) I was a bit paranoid & wanted to check everything. After the engine had been running for a few minutes the mirrors were wrm to the touch.
In case I needed confirmation in icy mornings they steam as they defrost!
If they have been missed off you could try and get some freebies - for the missing sunroof I got the original £500 knocked off, and an additional £500 as compensation, and roof chequers supplied & fitted FOC.
