Therma rest make different grades of mat and if you really want to be comfortable you need to get the expedition one, it's bulky but not too heavy and can be strapped to the outside of your kit in a waterproof bag.
For those of you having trouble sleeping in the great outdoors and sliding off your kip mat here's what I do (learnt the hard way after 25 yrs in the infantry).
1. Spend time finding a level stone free site, sounds obvious but most people don't bother.
2. Make sure your s/bag fits and that you have room to move inside without it drowning you. A hood, neck baffle and venting zips are imho a neccesity.
3. Down is warmer, lighter and more packable than man made filling but does not like getting wet sooo,
4. Use a bivvy bag to keep it dry and place your kip mat inside the bivvy bag, you are less likely to slide off it.
5. I use a small down pillow on top of my clothing and I often wear ear plugs especially at rallys/noisy campsites
6. Finally I sleep in l/w top and bottoms made from an old parachute, they are light, non sweaty and allow you to move easily in your bag.
PS have a bottle clearly labeled P do not drink nearby in the night soaking wet feet and down bags don't mix.