Those URLs have the same effect. And changing your "country of residence" is the way to do it on ba.com. They have recently lifted the restriction about the credit card having to be billed in the country of departure, but this has not
AFAIK yet been publicly announced. Nevertheless, I'm hearing quite a lot of reports of people successfully booking tickets ex-European stations with UK credit cards and having no problems in getting ticketed, checked-in and carried. Ditto US credit cards booking tix ex-LON.