In reply to kmabbsy:
Hi,
I had the Fission AR for a while but sold it as it was too much, to warm and sweaty for uk weather. The LT is windstopper so might not be as bad. but its still not all that breathable so I imagine its not going to feel much different, plus it only has 10g less insulation than the AR. If I were you i'd look into:
http://www.arcteryx.com/product.aspx?Solo-Jacket
I imagine that would be much cheaper and more suited to uk conditions.
ps: with Arc'teryx gear if you want something thats not on sale in the uk call or email Howard Carter at:
http://www.theoutdoorgearshop.co.uk
He'll specially order in anything you want at no cost, you can change your mind at any time and his services are excellent.