Thanks for the advice folks - most helpful.
I tried two different recovery packages, photorescue (as recommended above), and another called Imagerecall. However neither could see anything on the card whatsoever - which was a little depressing.
But I could see the files with explorer - so with some experimentation I discovered that paintshop pro would make a reasonable stab at opening them - some it wouldn't, a few without trouble, and a number of others it would open part of the picture and the rest was greyed out. Fortunately that way I recovered most of the more critical photos (if not about 2/3 of the remainder).
Having reached this point, of the main photos being useable, I've explored the cameras manual and discovered a semi-hidden format option that I didn't know was there. So, in partial victory I've reformatted both the MMC card and internal memory.
thanks again,
G