If you consider the amount of heat lost through the head then a hood is a definite 'good idea' for increasing your comfort when diving in cooler waters. I would also recommend some gloves and it might be worth investigating one of the thermal rash vests for wearing under your wettie. Try stuff like this http://www.adventureextreme.com.au/c...o.php/9/0/4/31 or http://www.radiator.net/general/categories.aspx if you can find them near you.

HTH