Well, I sort of figured out that I wasn't going to hear from the plasterer, so I suppose I shall eventually have to steel my nerves and give it another shot. Or wait until I make friends with somebody who knows what they're doing and have them come over and fix it for me while I watch and pretend to learn.

Your concept of the hole isn't entirely accurate, though... it doesn't go straight through up into the bathroom floor above. I'd guess there's about a foot of space between the opening and the boards of the floor above, and it's full of pipes and cobwebs and dust.

I do have one home-repair success story. When the ancient overhead light in my son's bedroom finally shorted out and gasped its last, I managed to purchase a new fixture, remove the old one, and wire the new one into place successfully. And I didn't even electrocute myself in the process! Go me!