We have tried and tested lots of bits and pieces over the few years we have been doing it.
We have done airbeds, camp beds, self inflating mattress, pros and cons with all of them.... but we have just spent a small mortgage on 2 Exped Megamats 10cm after reading the reviews on here, inflated them for the first time and they look and feel out of this world! We are giving them a go next week on a camping trip! Can't wait as I suffer with a dodgy back (2 surgeries later - so worth spending as much as you can afford to sleep well!)
Duvet/bag - well again we have tried and tested most options but find a double sleeping bag each works the best! Loads of room and very warm!
We use double duvets with SIMs, rather than trying to put a sheet on the SIM we put it inside the duvet cover and fold the extra duvet over.
To keep our heads & shoulders warm in cooler months I wrap a fleece around them like a hood which also acts as a baffle to stop drafts getting down the duvet.
To transport our duvets we use dry sacks which work similar to vac bags as you just squeeze all the air out, yes they cost more than vac bags but should last much longer.
Another vote for head torches. I wouldn't be without mine, great for reading by and indispensable when you need to use both hands to do something in the dark.
We also use 2 battery camping lanterns. They both have a remote control thingy so you can light them before you reach your tent - very handy when coming back from the pub in pitch darkness.
If it's very cold I wear a hat in bed. We have king size sleeping bags that zip together to make a big double, and fleece blankets over the top. We also have a fleece blanket under the sleeping bag for extra insulation, and foam-backed picnic blanket under the air bed so the bed doesn't get cold. I also like to pop a hot water bottle in the sleeping bag before I go to bed, so it's warm when I get in.
We bought thin but highly absorbent trek towels for camping. They take up very little space and dry quickly. A large plastic carrier bag keeps everything dry in the shower.