just returning to bushcraft and I need a new bivi bag, rather embarrassed as I think I may have unwittingly sold my old ex army one with a load of fishing gear hoping to get out in the next few weeks and have always used a tarp and bivi bag, currently using snugpak sleeping bags but is there bivi bag any good? not fussed about fancy hooped bivi's as I've always made do with army surplus bivi's....... TIA