Trouble searching with date format (US/UK formatting)

Hi all,

I have a report with a date field ('Created On Or Before') which, when the report is executed, gets a list of opened cases from the date before the value entered. This works fine only when the date is typed in mm/dd/yyyy format. If I type it in dd/mm/yyyy format, there is an error whenever it falls outside the US bounds of the date format (i.e. when I type 15/12/2014):

When a valid date is entered in MM/DD/YYYY format, the data which is returned (from Dynamics CRM) is in DD/MM/YYYY format. The data in CRM is all in DD/MM/YYYY format, including the 'createdon' field which is being searched in this report. The language of the report is English (U.K). Can anyone provide any tips so I can search in DD/MM/YYYY format?

Thanks