How to recover deleted data from erased hard drive?
Okay, so I think I've solved the problem and thought I'd post this up just in case anyone runs into similar issues... 

I've downloaded a program Data Rescue 3, and I'm scanning the drive for deleted files. The program seems easy to use although I found that if you want to scan your internal drive (as in my case), you'll need to have another external drive plugged in as the software won't let you restore to the same drive you're recovering from. 

When you run the software, select your internal drive to scan off then select the deleted files scan. When prompted, select your external drive to work off.

I'll post my results, success or failure, in the comments soon.

Screenshot of results: