The coldest I have seen Dutch was 39 degrees. In a dry suit it was manageable. My biggest issue with Dutch is worrying about those nasty ear infections, and of course those times of waiting in line outside the gate. I am by no means the most experienced diver, but there is so much history just off the coast I hate to waste a dive (unless I am training on new equipment) in a quarry.
I am not sure of you skill level, or your ability to use a drysuit, but this is a fantastic piece of equipment (one I will never regret buying) and should be the choice of anyone diving in cold water. It has its own bouyancy capabilities for diving doubles, and best of all......ITS WARM!
I do not mean to bust on Dutch, I am very very lucky to have this place with 45 minutes from my home, but I feel I am blessed with a 1 to 1 1/2 hour car ride to what I think is the best (in the $100 range) diving in the world. I may be a bit partial because I can not afford to dive Bikini of places like that, or fly around the world. I am pretty limited to where I can pilot my vehicle.
Good dives, be safe.