The version we chanted at school:

Twas Xmas day at the workhouse
and the paupers' hearts were glad
For the thought of the of the Christmas pudding
Nearly drove them raving mad.
Then out stepped the workhouse master from its grim and grimy walls,
They wished him "Happy Christmas"
But he only answered "Balls!"
Then up stood a brave old pauper, his face as bold as brass;
"We don't want your Christmas pudding,
You can stick it up your arse!"