An afternoon of poking around, and here's what I've found.
1. Despite some concerns, there's no sign of leaking around the power steering pump, other than the coolant I already know about (new top hose on the way as bleed plug is just shot), and general oil all over the engine bay
2. However, possible (/probable) signs around the steering box. What do you reckon from these? My power steering fluid had dropped, but I can't say for sure since when, and in the 100 miles since I topped it up it doesn't seem to still be dropping... so far. It does look like there's something leaking onto it from higher up - but of course its entirely possible that it's both.
Also
- purely in terms of the work of doing the job, not parts, how much of a pain is swapping the box? Better than doing the pump?
3. No picture, but suspect drive shaft seal has failed. There's a leak down one wheel, but gaiter looks to be in good condition all around, and brake hoses (all new last year anyway) also look good. Nothing else it could be?
4. What a blinkin' pain getting that glow plug connector back on was! No idea why it had come off, though