Hey Rossow!
We've got 2 x OzTrail king single mats from BCF - the big 10cm thick ones. They're great. Perfect for a cold night if sleeping on the ground, they let none of the cold come through. Amazingly comfortable. The king singles are easy enough to roll up, a double would be nigh-on impossible, but that's not what you're after. We store ours inflated with the caps off, I think that's one of the keys to keeping them working well.
I've got a bad back/neck, so I'm pretty susceptible to a bad mattress, but love sleeping on these. That's also the reason we went with the 10cm thick ones instead of the smaller hiking-specific ones that are only a couple of cm thick. They pack down a lot smaller, but I need the more cushioning of the fatter mats. Plus they either go in the car, on the roof or in the trailer, so size/weight when packed isn't really a concern for me!
Friends of ours came with us camping a couple of weeks ago, and they used our tent and the mats. Saturday morning saw it at 1.6 degrees at 7am, but I don't doubt it was a lot colder than that between 4-6. They were perfectly warm and comfy, Jan even tried to smuggle one of the mats home
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tldr; I'd buy a couple of the cheap OzTrail ones from BCF when they're next on sale, and give them a go. If you want to upgrade to an expensive one later, then you won't cry about retiring the OzTrail ones. Personally, I couldn't recommend them enough.
Good luck!
Matto