There is a problem with my post in part 1. The worst case scenario isn't that the publisher says no, it is that they say nothing.
This could occur if the manuscript or SSAE gets lost in the post, although that's unlikely. I may joke about them, but Royal Mail are usually pretty good.
The more depressing alternative is if the manuscript gets stuck in the slushpile and left unread. For a good assessment of how this could happen, see "The Sobering Story of Myrtle the Manuscript" by Tappan King. It's a good read, not just amusing but also useful for anyone considering writing. However it's a completely nerve-wracking article if you have a manuscript on submission. Be warned.
This worst case scenario comes with the difficulty of politely and delicately chasing an editor about a book, while not doing anything that might make them drop it.
This part of publication in general, waiting on feedback while racked with nerves, is what agents are good at. Since I don't have one, being in the rare position of selling my first novel myself, I'm learning as I go.
However, for prospective authors, it is worth remembering that if I had stopped trying when the agents said no I'd never have landed the first book deal, far less been discussing a second.