Well it seems that I've managed to fix the card mentioned in my previous post.
The battery arrived from eBay, I cleaned up the traces (and repaired where necessary) and the miggy now boots with the card in place. I think its looking pretty darn good:
With some identification help from the friendly folk at AmiBay this seems to be an RTC and 1/2 or 1MB RAM upgrade board (seems that the RAM chips are 256KB, so possibly 1MB). Now I need a new FDD or equivalent to test this baby out as I can't get disks to load properly. No one ever said a retro-computing hobby was going to be cheap...