Figured I'd take the chance to scan the room I've been working in with the thermal camera, given how cold it is outside. Most of it looked pretty much as expected but then I found a patch that was 25 degrees. That seemed pretty cold, so I took a closer look and found that in an obscure corner, behind a 9" beam, there was another gap in the brickwork. Just what I didn't really want to be finding, but a quick application of some cement seems to have fixed it. The cement isn't even dry yet and it's already showing 33 degrees there.
Then I figured since I was in a working frame of mine I got a can of spray foam and filled a few small gaps with it. Nothing major - one gap in the brickwork that I'd put fiberglass over because it wasn't producing a draft (there was a slight draft there today), and a few remaining gaps around the beams that rest inside the concrete blocks.
I should really get into the cramped space at the very end of the bedroom closet. If I can figure out how to get a saw in there to cut the last couple of inches off the floorboards I can dump some of my surplus cellulose into the space. When I look at the wall in the room below through the thermal camera I can see an orange strip, then a blue strip, then an orange strip. The blue strip shows the insulation has blown (and there are probably gaps in the brickwork there too, waiting to be found). One of the orange strips used to be blue until I dumped cellulose into it from above.