Hi there
Its hard to advise exactly, as you have not listed your TV's model number. However connect it all up this way:
- Connect your Virgin box to the TV via HDMI
- Connect the DAV-TZ140 to the TV via HDMI AND connect a set of composite audio cables (Left and Right - RCA) to the TV's audio OUT (they are Red+White coloured). Now, if your TV does not have composite audio out - things get a little more tricky (and I am unsure exactly if it will work) - You will need a cable that has two RCA connectors to a 3.5mm headphone jack - to connect to the headphone socket of your TV.
Hope this helps.
Cheers