Needle Sports have a load of Integral Designs bivi bags at half price.

Integral designs stuff is now sold under the Rab label which is presumably why they are getting rid.

Quality gear.

http://www.needlesports.com/Catalogue/Camping-Equipment/Bivi/Bivi-Bags

Must resist!

What does a £200 (reduced to £99) bag do that my £20 army surplus one doesn’t? Genuine question,what am I missing out on?

the differences are usually in weight and the performance of the material/membranes
so a £200 bivy should be lighter, more hard wearing and more breathable

hmm,
my Goretex bag is an army surplus one and cost me £20 too TINAS. 20 odd years old now. No zips, nothing to go wrong.

…but there again I do like the look of that cocoon bivi.

Hmmmm, yup, they do look a bit more ‘designed’ than the army one which is just a big rectangular sack with a flap at the top, and is quite heavy as it’s made from one material so presubably tough enough for the base and breathable enough for the top, but therefore double the weight of a thick groundsheet and thin top.

But if the weather’s crap enough to need that sort of thing I won’t be out (or I’ll put the tarp up).

I looked at those Dutch hooped army ones, nothing a matter with them except they weigh ~700gms more than the Cocoon ones.

Oh and reading around the eVent fabric seems to score the highest for breathability.

Went for a Bivvi in the Lakes a couple of years ago with two mates.
One with a cocoon, the other with a reasonably priced bivvi bag and me with my £20 ex army goretex bag. Guess who was driest after a night of drizzle?
The guy in the cocoon was ringing wet from condensation. The other was damp and I had a damp patch on my shoulder where I’d drooled.

One of the other difference between the expensive bags and the cheaper ones (alpkit, army surplus etc) is also usually in the closure design. the expensive ones will have more though and features, Alpkit / Army surplus ones are just a simple pull cord closure.