Scott78 - I have exactly the same symptoms as you. 2002 Octavia; intermittent loss of sound; radio is all powered up, cassette player winds tapes, can change and "play" CDs - but no sound whatsoever.
To begin with, the sound disappeared for a few days and then came back for a few days, but in the last couple of months, the radio has only worked once - for a period of about one minute! I've had the radio out, fiddled with all the connections on the back, but all to no avail.
I'd been assuming that it wasn't the wiring to speakers that was faulty, because either all of the speakers work or all of the speakers stop working simultaneously - it's not just one speaker that falls silent. But is my assumption wrong?
Would be very interested to know whether you have got to the bottom of what is wrong with yours.