changing decimal notation to comma from period

I would like to know how I can default to using european decimal notation, that is using a "," instead of a "." period to denote the decimal, and a "." instead of a "," to denote thousands (i.e. 1.234,56 rather than 1,234.56). This is important as my accounts use the european notation, so importing statements results in useless value entries. I have searched around, but I cannot seem to find any setting, or config file which covers this.