im pretty sure i remember reading that some merchants are capable of checking if a transaction passed an AVS check or not, even if a check was not possible I.E Foreign Card etc, it would return avs "not matched". Also would'nt the card type be returned as "Bank of France/Denmark" or whatever foreign card was used ?? In my experience if your gonna use a international card to buy something in your own country, try and do it early in the morning, pay for next day delivery and also try and pay OVER THE TELEPHONE. Theirs a chance they may just manually input the card info on a Card POS terminal which obviously is'nt gonna give them a detailed report of Bank/Country/AVS MATCH as say an online merchant processor will Sagepay, etc, etc.
Just my humble opinion

Good Luck.