Here is a map on countries that use decimal point vs comma: http://en.wikipedia.org/wiki/Decimal_point

"In the nations of the British Empire, although the full stop could be used in typewritten material, the point (mid dot: ·), which can also be called an interpunct (often referred to as the decimal point) was preferred for the decimal mark in printing technologies that could accommodate it."

Actually, that's more correct, the symbol to seperate whole units from tenths of units isn't the '.', it's the '·'. We had to have that drilled into us all the time we were at uni, because the 'dot' is actually the 'dot product', something about what you can do to matrices (7 years of engineering degree later and I still don't quite know forwhat it's used IRL). We had a maths tutor who would mark us down for using the wrong symbol in the wrong spot. (although that wikipedia article seems to put the dot product in the middle of the line too. Maybe i'm confused and it's a 'dot' that we had to use for multiplication because we couldn't use 'x' in algebra. I'm definitely confused, i'll have to check my maths textbooks next time I swing past my mum's place.)