Thanks again for the help, I think I I will try to proceed with the pywallet recovery tool.
I looked at that when this happened initially, purely becuase the Bitcoin client said the wallet I was trying to load was in the wrong format.
I didn't get it working & came here for help.

Thanks to you all & if I get the wallet back there's something for all that helped.

I am not holding my hopes up of finding the key but I won't give up.

I'll tackle this job sometime this week & post back.