Pretty much mate, there are some good free recovery utilities out there.
I would try something like getdataback, although that is paid software, there is a free version so you can at least try it and see if it will recover your data;
http://www.runtime.org/data-recovery-software.htmI would also be inclined, once/if you get the files recovered, to copy them, then format that external disk and run a drive checker on it to make sure the drive isn't faulty before you use it again.
Let us know how you get on.