Because I have no patience and no fear of software I totally trashed everything by mucking about with shelves in a fairly hasty manner. So to fix, I thought I would delete all my books and shelves and do a complete re-import of the GR export file.
Now I have no books, no shelves, and an import from GR that BL thinks it's already done and won't do again. I even managed to trash my GR account as the BL changes were pushed back there. Go me!
Oh, well, I know the BL team will sort it out for me, and I've done a complete delete-and-re-import on goodreads too.
To celebrate my intrepid explorations, I will start a new book! Trying do decide...