Thank you so much for your interest and response. I think that I followed all the suggested 6 steps from the iBA user tip but to no avail. Do you know anything about this comment by dmingo which is pasted below?
'User dmingo says this about that:
After audio tracks are placed in your book, you must 'Publish' the book from iBA (using the 'File/Publish...' menu) - that means re-entering all metadata from scratch - you can't simply import the .ibooks file into iTP. If you enter another audio clip at some time, you have to do it all again. '
To me it seems to say the video clips need to be delivered separately and one at a time.
I would be grateful for any advice