The same. Its shows as 03-Jul-12 in the cell but on the merge as 7 March 2012. Unless I put 13-Jul-12 then it becomes 13 July 2012.

It seems as though it is something to do with the merge field code as if I just add the field without amending the code it comes up as 03/07/2012 or 13/07/2012. But when i add code it seems to confuse it even if i put code in the same format as the default (\@ "DD/MM/YYYY").

If it was either US format or UK format all the time i would think it was just something i was missing but the fact that if after 12th it switches is weird. Surely if it is set to US as it appears to be that when you put 13/07/2012 it would create an error.