I recently bought a Czech bed roll, outer is supposedly water resistant, the blanket is I think synthetic fibre, and it comes with a very thick and remarkably robust (feels like heavy cotton) liner.
Another forum member said recently, ' kilo for kilo not the best warmth provider ' or along those lines.
I tried it out recently in 3-4 celsius inside a tent, and I was wearing lots of very warm clothing and had a hot water bottle (hoping that would bring ultimate luxury).
I was very disappointed, I will probably never use it again, all weight and no warmth, waste of money as far as I am concerned, it was only £15.00 delivered, now I know why it was so cheap.
I would say that the inner liner\sheet is the best part of it, you could tar it and make a coracle skin with it.
I might (and only might) keep the outer as a bivy bag, I do not know if even that is waterproof\resistant.
Maybe I bought a duffer, but I regret to say it is extremely disappointing.
Sorry for the negative post, but I am being honest.
rorymax