In reply to Double Knee Bar: In their product categories, Alpkit products normally are the best value for money you can find because their business model misses a normal link in the chain - retailers. So you may well be unlikely to find a similar bag for a similar price.
This makes Alpkit great, but the downside is they seems to have problems knowing what amounts to order (I guess a 'normal' manufacturer would manufacture set amounts based on forward orders from shops?) and hence there are many products on their website that they are not actually selling currently. There have been a couple of things that I have wanted to buy recently, but I've had the same experience as you - finding they are not in stock and Alpkit aren't always sure when they will come back into stock. The product is there on the website, but you just can't have one! That's a bit annoying - I wonder about the logic of having lots of products on the site that you can't actually buy.
I was reading up on sleeping bag testing for the S2S and Marmot bags I was testing this winter/spring for UKC (
http://www.ukclimbing.com/gear/review.php?id=3747; http://www.ukclimbing.com/gear/review.php?id=3605) and it is interesting how many brands are now using the EN 13537 standard. I hope Alpkit might also in the future, just because it would make it easier to compare their bags with other bigger firms. They use a British standard that might well be great, but unfortunately it makes comparing a bit harder.