Hi all - just to pass on what I've found.
On Windows you can write a ".bat" file to rename files in a folder. Its pretty tedious to set up but once done you just put the ".bat" in the same folder as the file names you want to change and double click on it. You might have to refresh the folder contents to see the results. You MUST do this with Notepad or other plain text editor - not Word. The rename command is simple:
ren current-file-name new-file-name
That's all. "ren" *space* current-file-name-with-extension *space* new-file-name-with-extension.
Obviously it's a pain listing things from a folder like this but if you are going to be doing this often - you might be able to reuse the "bat" making find-and-replace changes.
On the Mac side I heard of an app called "Better Finder Renamer" or something like that.
I'm still not happy with this as a solution. I'd rather learn of a way to make PShop do the numbering as it saves files.
Thanks Paul - that solves many of the issues I'm having with these batches.