Anybody had their audio volume disappear on them? Cant hear my tunes, radio or directions etc.

My SatNav CD and aux all technically working fine on my RR L322 (03 Plate) but the sound suddenly gave?? LR say it's the black box unit below the satnav in the left hand boot space.They want a fortune to replace it

Could it be a loose wire or connector problem? Anything I can press or prod to cure the cabin silence....

Help - advice please