This is a right pain Steve, but I have been writing my questions as best I can in my test Moodle and then backing them up, using the backup when I want them in my current production site. (I move around a lot.) I used to convert everything I could to the GIFT format and use that to upload, but from memory, that did not always work, which is why I now use my test Moodle.
Also, doesn't BB have an option to convert questions to GIFT or similar? Using the find/replace in Word should help save a lot of time and saving the file in a txt format for conversion to a csv file should complete it. Alternatively, can work save a file in an XHTML format? XML Angel is new to me, but Moodle does have a builtin XML Format file handling capability that can be used for quizzes. Also, xml, xhtml and csv files can be opened in something like NotePad++ which also has an excellent find/replace function to convert questions to GIFT.
I suspect that whatever you do, it is still going to take some time to complete. "To convert or re-write, that is the question"... up to you unless someone else has a better idea or can provide an option.