Once I'd done that, it was pretty clear there wasn't enough in my manuscript about the main plot. In fact, it was mostly subplot, and while the subplot/s are interesting, they're not enough to draw the reader through the book.
I've decided to add an extra day into the timeline to put in more plot related scenes. Some more investigation of the two heirs should do the trick. I'm also working out which subplot points I raised earlier need to be closed off as well.
Doing all this should bring my word count above 80000, which is what I'm aiming for.
Now I just need to write the thing. Man, it's hard to write when you're tired.