K11 engine fuse box how to gain access?

The 80 amp main fuse has gone in my k11. I got the top of the fuse box off and can see it has melted. I want to change it but I can't get the bottom off to gain access to the legs of the fuse. There's a couple of clips that I've managed to release but there seems to be another clip inside the mount somewhere that I can't see. Any ideas?