No problems within the defined rules, although occasionally ticket sellers do not know them so well as we do. The ticketing must be completed in the country of origin, but that is just where the seller's office is located, not the purchaser's domicile nor the country of registration of her credit card.

Try using http://rtw.oneworld.com to get an idea of pricing, but please note that the website does not show all possible flights and will insist that you must ticket with the first carrier.