I seem unable to delete some mismatched items. I have followed the instructions but no remove button appears when I select the item in owned movies. I would appreciate advice
Cheers

When you've reached the page of the movie, you must click the "owned videos" box, to select which video you want to remove (you can have several videos of the same movie). A window describing the video will appear, and at the bottom right there's a button "remove from owned".