Today was very productive. The engine's pretty much together, so it should be no problem getting it fully together by tomorrow. Depending on how confident I feel I might even turn it over.
I started off the day by fitting the fan belt and alternator, followed by the air pump. After lunch I fitted the distributor, although I've yet to work out how to check if cylinder one is in it's compression cycle easily, so haven't been able to set the timings yet. The Haynes manual suggests feeling for pressure on the spark plug hole, but it's too far down for my dainty fingers.
Once the last of the large components were installed I could start fitting the hoses for the cooling system. During this I realised why the heater never worked - the hoses that go off the the heater matrix has been bypassed with a length of copper tube. I'm hoping that this was to improve engine efficiency (the coolant can't have been flowing well, given that the waterways were completely clogged), but it might be that I need to work on a new one soon.
The only bits left for tomorrow are the hoses for the brakes, finding where the choke vacuum hose goes to and getting bits adjusted where possible.