Good point about 'sleep systems.' I used to buy a mattress, sleeping bag, pillow and sleeping clothing separately without regard to how they would work together.
When I realised the importance of harmony my comfort and warmth, etc improved considerably. So I thought groundsheet, tent base material, mattress, in my case a sleeping quilt, pillow, sleeping top and sleeping bottoms, if they work well together, great, if not I'm always going to be dissatisfied with my lot. I've now moved onto a sleeping overthrow blanket as well for the winter months. It should be a down sleeping overthrow blanket but I haven't found one yet at the price I want to pay.
I am also looking for some kind of cheap low weight rollable insulating material to go immediately under my mattress, again for the winter months. I remember someone wrote into the Forum a few months ago with a suggestion that B & Q may have a suitable item but I can't find the suggestion brand name at the moment.