OK - both problems are solved.

I soldered up a replacement PRAM battery from two new VL2330's and that is working nicely. And using the donor machine's top half i.e. trackpad & button, I now have a fully working 1400c again. Well, except for the dead main battery pack of course - that's next month's project.

Of interest, the newer of these two 1400s was manufactured in July 1997 and has two PRAM batteries, whereas the older one, manufactured in Feb 1996, only has one. As I only had enough VL2330's to make one replacement battery pack, I've left the second, dead PRAM battery unchanged without apparent ill-effect.