Well, I did test the fuel system. As discussed, the plan in the absence of an engine was to connect the outlet to the return at the filter, and test it recirculating:
Good news: the pipes and hoses are all fine, the pump works without strange noises, and a healthy volume of fuel seems to be pumping around.
Bad news: yet another unplanned fluid spill on the garage floor. The allegedly refurbed pump is pissing fuel from somewhere. Gah!
I've ordered some replacement O-rings in the hope that it's a simple fix up at the pump end (as opposed to the motor end). There are two O-rings there, easy enough to access (4 screws, which I'm sure won't be corroded at all...). But if it's not leaking from there, the whole thing needs to come apart, which seems to involve a fair bit of faffing about bending back retaining tabs, de-soldering connectors etc. I'm told there's no guarantee of success; some of them just seem to leak no matter what you try.
I also have a minor head injury, which often seems to happen when I work under a car. And no engine. And a total of one working brake caliper currently fitted (others all leaked, at least one of which was due to my own incompetence).
So, not going so well this week.