Just a quick note to say that we're pretty much back to normal. I've finished restoring all the posts that didn't import properly (the comments I've left for another day, as they're not so straightforward), and fixed the various planet URLs I'm syndicated to.
It's been a pain in the ass to have to migrate everything off a self-hosted, old, crappy desktop+server to a real server and then to blogger, but thank god I'll not have to do this again.