I have been working on this and have come up with something. OK, it's not what I originally planned, but it's something to start off with that I can add to. What I have come up with is:
A fleece sleeping bag liner that I bought for £16 locally.
A wool blanket that folds up pretty small and is versatille.
A reflective blanket. I think its called a sportsman's blanket in the US. The only other one I've seen in the UK was in the local shop as I got the fleece liner and cost £20. I didn't buy that one, but I saw this one today for £5 so I snaped it up. It is a ripstop aluminised sheet on one side and blue tarp on the other. It has a strong edge around the outside and big grommets at the corners. This could be used as a tarp, groundsheet or as a sort of bivi bag. Maybe in the future I'll cut a hole in the middle to use it like a poncho as originally stated.
In the bedroll there is also a piece of closed cell sleeping pad about 1/2 normal length to go under my torso. All this fits into a OD nylon stuffsack which, useing the drawcord and an additional piece of cord, is tied into a hudson bay pack so it can be strung across my shoulders like a traditional bedroll.
I haven't yet used this outdoors. When I do, i'll give feedback

I still welcome anymore ideas.