Octavia Mk1 Symphony Radio - all head functions ok but no sound

Radio/Cd worked fine when we first bought car, then all sound disappeared, came back after a few days and has now disappeared permanently. All radio functions seem to work, seeks/finds stations, volume control works but no sound. removed head unit and tried alternative radio - same result. All seems to work except speakers. Checked fuses - both one in head unit and one in fusebox are ok. My only thought is that there is a multipin speaker cable connector down line from the head unit where speaker wiring splits to the separate locations and this has separated?? - but as i dont have a wiring diagram i cant be sure.

Anyone had this problem and any ideas?? - or knows if there is a speaker wiring connector down bwehind the dash somewhere?