If you're on the look out for a lightweight insulating top, the new vest from Borah Gear could be worth a look. 50g of 850fp water resistant down, 10d Argon outer shell, total weight 100g and $99.99 or £60 in proper money.

http://borahgear.com/vest.html

Import duty? £66 shipped otherwise. I had one almost paid for with paypal monopoly money until I thought of duty+VAT (

I have one and a cuben bivy already ordered. Will feedback when it arrives