O, what kind of nice collection!
And I just had a coffee after a good night's sleep!
I think, that British army bivvy bags are good for colder British weather. Tough but relatively heavy. I have a green one and like it, but:
The Snugpack Special Forces Bivvy Bag is far lighter and I find it very comfortable too to use this central zipper to enter it. In hot conditions the zipper is necessary. There is a reason, why the French and German army uses bivvy bags with central zipper. In the summer on the continent it simply becomes to hot in the closed goretex bags.
I have tried a few, stuck with rather less. I can't make a reccomendaion about these two. They just happen to have been caught up in my attentions for a few months
The Outdoor Research Bivvy Tarp and the Outdoor Research Bug Bivvy.
They both have had good reviews from people I know who have them. The Bivvy Tarp is a likely purchase for me. The Bug Bivvy, I don't like need need, but it is so insanely convenient and will be great for watching space junk float by in the early hours. So, I guess it is just as likely a buy