The Slade song youre referring to is actually called
Merry Christmas Everybody . . . and if it were not played to death every blasted December in the British Isles and beyond, it might be tolerable.
The other song that gets played to death over there is
I Wish It Could Be Christmas Every Day by a band called Wizzard (lead singer Roy Wood, formerly of ELO). Those two songs get played so much together, they begin to meld together after a while . . . total horrors.