The C of E reigns. The survey probably merely reflects the fact of immigration from former colonies that are not traditionally Christian. I wonder what the numbers would be among white, anglo-saxons. I've noticed a backlash in the states against "Happy Holidays." People who never would have made a point of it before (including me) now go out of their to wish a holy Christmas or Merry Christmas.
Season's Greetings always sounded so elegant. Happy Holidays sounds so commercial.