I will be using it for mountainering, so a tube tent or poncho is not a option. I want a really small, affordable two person bivybag. The lack of extra clothing and sleeping bags, means keeping each other warm is importent.
The Oware one looks ok, but the price is a bit to high.
Please correct me if I am wrong here, but I read your comment as the bivvy bag would be a substitute for warm clothes and sleeping bags??
The bivvy bag is an emergency option, not a substitute for clothes and sleeping bags. The bivvy bag is, as you probably know, not insulated.
The bivvy-bag ( a "windbag", "vindsäck" in swedish, "vindsekk" in norwegian) is almost a compulsory item when travelling the mountains of the north here, (Sweden, Norway and Finland) during all seasons.
Over here there is quite a range of different bags but I still prefere the brittish ones;
I own and use this one, check this out:
http://www.outdoordesigns.co.uk/products_shelter_group.html