Charlie Jefferson:Thanks for that.
I posted the question before I bothered to look around the back of the PS3, and yes you're right, the optical option is available.
Just need a long, long cable to connect the two devices. Calling Maplins . . .
How long is "long, long"?
http://www.futureshop.co.uk/qed-performance-toslink-digital-optical-audio-cable-10m-p-1182.html