After fitting the lower chrome finisher for part 8 I realised that it was a little out of alignment with the trim panel. It protruded beyond the door trim at the door hinge end and was slightly short of the end of the door trim at the arm rest end. On closer inspection I'd fitted it upside down. Easily remedied. It now fits properly. It's not possible to fit the upper trim panel incorrectly.

... and for some reason my part 9 came with the seat back already attached. One less job to do!