Finally got a response from BA Turkey (Bremen) on my DONE5 which had been prebooked with BA RTW USA:
Code:
DEAR MR MIAMIBEACH
THE ROUND THE WORLD FARE FOR A DONE5 FROM TURKEY
IS EUR 5999.00 PLUS TAXES. AS YOUR BOOKING IS
MADE IN THE USA WE HAVE TO COLLECT THE FARE FROM
THE USA 9200.00 USD PLUS TAXES.
SINCERELY BRITISH AIRWAYS TURKEY
THANK YOU FOR CHOOSING BA
So not only are they trying to charge me the USA fare (they are saying it needs to be
booked in Turkey, not in the US). But the fare is now EUR1000 more than on WearyBizTrvlr's spreadsheet! Back to square 1 for me...