Huzzah! In one night (and after quite a day), I have produced my first ever Wordpress plugin.
It’s still under development (needs to be added to the admin option panel rather than just running every time), but it automatically imports Livejournal posts into Wordpress, and not the other way around as most plugins want (post to Wordpress, auto-post to Livejournal). This is what I want (LJ is my primary publishing tool).
It needs more work, but not at this time of night…!