While the hob is still laying outside in pieces, I am at least back up and running with my PC. Most importantly, with all my data still intact, just where I left it.
So what had happened? I’m still guessing as to the exact cause of the failure, but the problem was a blank partition table on the disk, and a corrupted MBR. Under a hexdump, the ascii in the boot loader looked really wrong, and more like a snippet of my Xorg start up log than lilo, but the real killer was the fact that where the partition table should have been was just a lot of zeros, meaning I couldn’t mount any of the partitions to rerun lilo to fix the bootloader.