C70 Electical Short Problem

I have a C70 2000 Registration and the battery keeps being drained. Anyway i think i may of found the problem its either the lights or the volvo cd player i have installed, i.e. when the head unit is on and i turn the headlight switch on the LCD radio display flicks on/off at the same time as the light switch is switched from off on to sidelights. Has anyone got any ideas how i can solve this? Does it sound like a radio or headlight fault and any ideas what i can do to quickly solve the problem?

I think this is normal the radio display should dim when external lights are turned on.

look at the sun visors 

Cant say for sure, but my passenger side sun visor bracket broke over time and the wire for the vanity mirror light runs right through it. The wires stripped of insulation and caused a short for me as well No idea if its linked to the others but worth looking at.