And on to the tiling. Once again, trying to lay a rectangular grid onto anything in this house reveals the curvature: what started as small gaps between tiles ended up as quite large gaps by the time I'd tiled my way out of the back door.
Speaking of which, I thought I'd been quite cunning. I carefully opened up the patio door so that I could lock the back door and re-enter the house via the patio door, without having to cross the still-drying tiles. Turns out, though, that the back door won't lock from outside, so I had to resort to flipping the bolts with a long stick.