Thanks Dimitris, you're right but I was hoping the TVonics box (DTR-HV250) might work as a kind of HDMI switch taking sound from an HDMI IN and sending audio through to the SCART OUT but TVonics have confirmed that this is not possible:
"The DTR-HV250 will just pass through the HDMI from input to output. Audio will not come out of the SCART from the Incoming HDMI source.
For normal viewing of the freeview terrestrial signal. The HDMI to DVI lead will give your TV video and Audio will come from the SCART via the necessary LEAD if the TV will accept it as an audio signal to accompany the DVI input.
If you wish to hook up a PS3 using a HDMI Lead the TV will give the video and the audio will have to be supplied from the PS3 via the necessary lead."
So my problem is now here:
http://forum.beoworld.org/forums/p/25244/246913.aspx#246913