Apologies for this noob question.  The search function keeps timing out when I try to search for clarifying threads.

I'm working on 5-021456-168729 (not in db yet), an 18-disc boxed set of "Taggart: 1983-1992".  The early Taggart episodes were originally broadcast in three distinct "parts".  Each part has its own distinct cast list at its end, which differs slightly among the three parts.  For example, some characters who appear in Part 1 do not turn up again, while others debut in Part 3, and the ordering differs even for those who appear in all Parts.

On the DVDs, these have been presented as one Episode per disc, with each originally broadcast Part separately selectable from the root menu, but the entire Episode can be watched via a "view all" menu item (the viewer will see the credits ending each part before it proceeds straight onto the opening credits of the next part). 

These episodes have been entered into the database before, such as in 5-021123-111249, with just the one division per episode. (For all I know, that may well be how that specific DVD has been produced and the cast list in the database may well be a faithful transcription of what has been provided).  However, I have noted a very few omissions from the cast list of some cast members who do not appear in all three parts (and again, for all I know, this may be how that DVD has been produced and not an omission in the submission).

If I go the same way, how should the order be determined?  Unless some subjective judgement is made, some more important cast members from the final two parts may end up below peripheral characters who only appear in the first part. 

My preference is instead to list the cast of each Part individually.  If I use a divider for each Part, I'm not sure how the dividers should be labeled.  The DVD menu has just "PART 1".  Would dividers like this be acceptable? 

5. Death Call: Part 1
...
...
5. Death Call: Part 2
...
...

Or  should it be like:

5. Death Call
Part 1
...
Part 2
...