comfortable, wide, thermally insulated mattress
quilt for when it gets cold - a summer quilt will be fine down to 13degC, an opened out 0degC sleeping bag can be used for temperatures down to zero when used with the electric blanket solutions
something to cover your head and perhaps feet (eg. thick woolen socks) if temperatures drop below 13degC
eye masks and ear plugs or noise cancelling headphones to help you sleep - even if no people are around, the wind causing tent flapping noise or the birds can be too noisy for sleep
optional: dust or N95 mask if it is going to be windy and dusty
guy ropes and pegs (plus heavy duty angle iron sand pegs if going to coastal sites with strong winds forecast)
take a dozen or so clamps to allow you to clamp back the doors or the fabric inners etc to give visibility and to stop them flapping around
add some small carabiners to the guy outs to make it quicker to add your own guy ropes
take a spare 2.4x3m or 3x3m tarp and 1-2 tent poles to add extra wind protection options as below
optional: clear PVC sheet (queen mattress protector works well) to drape over inner 2P tent for further wind chill protection (may need to use 6 or so clamps to hold it in position for maximum protection)