Unfortunately the problem at O Side (as you know) is a bit compounded as they do not let you in the water until the wave before you goes off. So three minutes is all you get. I've found it helps if, while waiting for the wave ahead to go off, you sneak down the ramp as far as they let you, scoop up as much water as you can and splash your face continually, and get some down the suit. The suit works in part by warming a thin layer of water, so getting that water warmed up if you can really helps that initial shock

Agree wholeheartedly that keeping the forehead warm is key