another thing bring some warm tea/coffee in a thermos and drink that before/after the dive and during your SI that should help warm you up. As for my feet I wear a pair of 3mm neoprene socks next to my skin with a pair of wool socks and never get cold feet but growing up in the prairies well its hard to make me cold enough to complain.
why neoprene?
I think that would keep any moisture next to your skin, wouldn't it? I suppose it doesn't matter though, if you are not cold then you achieved your goal