I assumed that British (and Australian) people of Anglican or Catholic background would know about St Nicholas since Anglicans also have (basically the same) saints as Catholics.
About half the Australians have at least partial Irish ancestry, but the Irish seem to be the only European Catholics that don't celebrate
St Nicholas' Day. Even Orthodox in the Balkans celebrate it. Australia also has plenty of Southwest German (the wine makers), Italian and Greek immigrants who all should know about St Nicholas.
One may not believe in saints or all that Xmas crap, but contrarily to most Christian dogma/fairy tales, saints were real, living people who were beatificated by a pope. So St Nicholas/Saint Nicolas/San Nicola/Sankt Nikolaus/Santa Claus or whatever his name was a historical person, a citizen of the Roman Empire.