And managed to get the car up on a lift today to take better pictures. Look at the amount of gear oil under here..
Bigger image:
https://picasaweb.google.com/lh/photo/RwAGHy3zOi7mpVbBJzDEsw?feat=directlink
As for the vibrations, it wasn't a balance issue. Look at the tyre that was on the back:
No idea what has happened. Maybe the tire is just very old? Anyway, not safe. I've replaced it now with the spare tire for now. All the other tires were fine..