PO Form - Euro number format

Hi, we are printing PO's and standard PO forms issued to supplies in other countries have a standard number format of 1.000,00, whereas in the UK we have 1,000.00. When we actually look in the transaction we see it in the UK format. Is there a way to modify the form that comes via the PO message function to always print numbers in UK format, regardless of the country the supplier is in? I am sure there is a tick box somewhere but can't find it!