I put a picnic blanket (the kind with foil underneath it) on top of the groundsheet in the bedroom. Depending on the weather, I sometimes add another blanket to that.
Then either my SIM or the folding camp bed (I invested in the bed 3 years ago - not entirely convinced yet as only tried it for 3 nights and 2 of those on Cub camp - but not my best sleep ever).
I have a 4 season sleeping bag, a small pillow, my hot water bottle, a woolly hat, fresh dry thick socks, and a further blanket on top.
I hate the sleeping bag - it's mummy style but I can't move in it.
I am actually thinking about bringing my duvet on my next Cub camp trip - they never see my setup anyway, the 2 male leaders think I am a wuss anyway because of the HWB but just gently mock me for it as I fill the burco after dinner - for loads of hot choc for Cubs, gallons of tea for Leaders waiting for Cubs to get to sleep, and finally my HWB with the dregs, (and they know that, as the "Mammy" Leader, I'm the one the Cubs will wake in the middle of the night so need the sleep when I can get it). And as we have a decent sized van for most gear, I can bring whatever I want personally in my car on my own (1 leader drives the rental, and the other 2 each bring our cars - as transport can be very useful for all sorts of reasons!).