Just a finisher for the thread ... for future reference.
Stat housing takes a bit of a tug to remove from the water pump pipe, but does indeed just pull off.
I noticed after putting it back together that it was still wet underneath where it joins that pipe - but after a bit of careful observation I noticed it was actually the small-bore hose on top of the stat housing that wasn't sealing properly anymore (looked like it'd never been removed, and had probably expanded that little bit to keep pace with corrosion of the metal over the years - scrape corrosion off, ID of hose now that fraction too big).
One nice tight Jubliee clip plus a mental note to replace the hose at some point, and coolant seems to be non-leaking now.
Lovely and clean down that side of the head now, what with bust heater hose cleanup, VTEC gasket and cam seal too recently!