You've got a short firstl ou need to find out where from if check the rear brake light but to me sound like somehting stronger as such draining all the power.I have spent a good few hours on it this afternoon stripping all the stuff around it away (windscreen wipers, various panels etc..)
The battery keeps going flat - I am guessing this is because there is a short somewhere? The fault came back as CC.0 which means it is earthing so could this be responsible (apologies, I am s**te with electrics)?
There is a fair bit of oil around the fuse box area - this isn't a good enough conductor to course a short is it?