my 6/5/4 has done the trick for me... 7mil sg5 boots, 7mil xcel drylock mits. I dont remember ever being cold... I mean I know its cold out but I never was affected by it that I had to bail or anything.
As for changing.... well I live at the beach so its basically just taking my mits and booties off in the backyard and then heading in for a hot shower.
being warm before you hit the beach is key.move quickly and keep moving,paddling,taking waves until adrenaline kicks in.after surf,who cares?if it's freezing,drive home in suit and change in the house.
throw some jugs of warm water in a cooler for the after session hose-down. or just do your changing at home. not sure why everyone feels the need to change right there and then... just throw a towel down and ride home.