Except, if you look carefully, the area of south Dorset round Weymouth and Dorchester (well actually we have a few patches of a thin scattering of snow and that only came on Wednesday). I don't think either 1963 or 1978 blanketed the whole country and, although I was eleven at the time, I can't remember all that much about the 1947 freeze-up.Satellite pic: http://news.bbc.co.uk/1/hi/in_depth/8447023.stm
Not sure of the last time every part of the country was under snow.
Mike.