Ok so to cut a long story short, my Linux server died, so I bought a caddy to get the data off the hard drive. Put the drive in the caddy, connected it up, but OS X picks it up but wont read it.
Nope. Mac OS X doesn't understand any of the extX family of file systems. However, Google is your friend for this sort of thing - it found this helpful forum post, among other things.
Hey guys, yeah I had a look at ext2fsx and that forum post, but I got an architecture not supported error. So I just fired up Windows and got a Windows-ext driver instead, cheers guys.