IF I remember correctly, in the UK they say Happy Christmas. Is that right snugs?
Snugs is stuffing her bird {see #14}.
We say both Merry Christmas and Happy Chirstmas. Though we tend to say Happy Christmas more.
I think we say Merry Christmas if we include the New Year greeting such as on a card which would read Merry Christmas and Happy New Year or Happy Christmas and a Prosperous New Year.
Strange how traditions are nearly the same but slightly different such as your Christmas Eve is more of a family and feasting than ours but then we get Boxing Day as a second Christmas Day.
Also you tend to refer to Father Christmas as Santa.