I think it asked to reformat when my son went to use it for the first time with Windows 8 and he must have done so (why does it ask to do this!!!) ... is there some way to recover the files?

Did you set up File History on the external drive to back up the files?

If you have setup File History, you may refer to the article to restore files or folders using it:

Restore files or folders using File History

http://windows.microsoft.com/en-us/windows-8/how-use-file-history

If you have not set up File History, you may need to use a third party program which could help you in recovering the lost data.

Note: Using Third Party Software or Link, including hardware drivers can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the use of Third Party Software or Link can be solved. Using Third Party Software or Link is at your own risk.