You're looking at a tough situation. From what you say you've already done, you may have already overwritten some of the old data when you did the recovery and put some files back onto the drive.
I'm not sure how the format function in the webinterface runs, but it likely just overwrote the main inodes and journal files of the disk, basically the index of the entire drive. The data is probably still on the drive, but it's floating out there without any references and no way to directly access it.
The proper way to do this is to image the old drive onto other storage, and store that without fear of harming the old data. In the real world, sometimes you don't have that much space, but definitely try not to put the recovered data back onto the drive because you'll end up overwriting stuff that you might have otherwise recovered.
You can start by learning how to use Sleuth Kit at http://www.sleuthkit.org/
. Sleuth Kit will go through the drive and pull out any data segments and organize them. In some cases it can even reconstruct the directory structure. The Autopsy Forensic Browser will make it easier for you to search and organize what you find. Both tools together can help you recover some data.
There are a lot of variables with this, including the biggest one that files can be fragmented across the file system, and it's hard to put them together contiguously.
You will definitely recover some information, hopefully what you need. The tools also help you grep through the information, so if you remember the filenames, words or phrases in the data you want to find, it will definitely help.
Good luck, I've done this several times and it's not fun