I found this on the web about French punctuation rules: http://www.interpc.fr/mapage/billaud/ponctua.htm
If my french is good enough, it says "only one trailing space for period and comma", but leading and trailing spaces for exclamation marks, question marks, semicolons and colons. In short: if the punctuation symbol is drawn with two strokes, put two spaces, if it is drawn with one stroke, just put a trailing space. It says nothing about the witdth of spaces though, but this thread does:
It seems that   is preferable as leading space with a regular space trailing.
More info can be found here: http://forum.wordreference.com/showt...73#post3063773