Lucky for me someone on eBay was selling spare keys (though at US$3.99 a key? Someones making a little money there), stems and springs. Have replaced three keys that were completely broken off. A bit of a scrub of the case in the sink to remove grime collected in and around the cases... I also bought a couple of LED's - I'll replace the missing one - even though it doesn't work... Well, its gotta at least look complete! lol!

I'm considering getting a Keyrah and making these into USB keyboards... And possibly thoughts on a Raspberry Pi emulator project. But we'll see...
Just thought I'd post a few piccies.
Pre-repair...
https://www.dropbox.com/s/mkzcbup956piify/64_KB_prerepaired.jpg
Spare parts...
https://www.dropbox.com/s/y23c5xfedpmxv5x/64_KB_SpareKeys.jpg
https://www.dropbox.com/s/5krun0gaoa0dmxc/64_KB_Spares.jpg
Tada! Now with all in place...

https://www.dropbox.com/s/9ckoezdd28hx6f1/64_KB_repaired.jpg