No Sky sound from back speakers

[Tarebare30]

Hi. I have a LG HT752TH home theatre system. If I play a DVD on it, all of the speakers work exactly as they should.
I want to use it with my Sky+ HD box and so I have connected an optical cable from the home theatre system to the Sky box. The Sky box is connected to the TV with an hdmi cable and the home theatre system to the TV with a scart lead. I put the home theatre system on AUX OPT and mute the sound on the Sky box to use the speakers, but I'm only getting sound out of the centre speaker and the two front speakers - no sound from the rear speakers. In the Sky box settings I've got:
Audio Output - stereo
Digital Audio Output optical - Dolby D
Digital Audio Output hdmi - Normal
I'm watching Sky sports and the show is in DS.
Any ideas how to get the sound out of the back speakers?
Thanks

 

[Tarebare30]

Got sorted. VSM and XTS Pro sorted me out