Sagem HD45 Sound

Hi, I have the original Sagem Hd45 (no freeview tuner) I have a home cinema system which uses optical, not coaxial, so I cannot use the SPDIF feature.

Due to the picture processing the screen does I cannot plug my Sky+ directly to my hiFi because the audio will be out of sync. So I have Sky connected to the TV using scart and the Hifi out of the TV connect to my home cinema system.

I can get normal analagoue TV stations sound coming out of my HiFi but when I am watching SKY, I still get the BBC1 sound, not SKY.

Could somebody please test this out to see if it is a problem with my set or a design issue.

Thanks