In reply to ACollins:
I strongly advise not bothering with the lidl inflating mats. I bought something similar and it was rubbish.
I do still have an army surplus one which has survived 15 years of mud and abuse. I eventually treated myself to a thermarest which is nice but not essential.
I bought a teeny one that packs down small and use clothes for my feet. If I'm car camping I take the foam mat as well to put under it. If I'm bivvying I take a smaller karrimat type to protect the thermarest and bivvy bag. Having got a teeny thermarest it fits in my bivvy bag which is good as I tend to move in my sleep.
Alpkit ones look good but I haven't tried them. Search UKC for reviews.
The lidl sleeping bag liners may be OK, I haven't seen them to check.
If you want a thermorest there seem to be a few on the ususal auction site.
Post edited at 22:51