after phoning the ONN company they recomended we use a headphone socket, as the audio output.
is this a viable option, and if so what would i need?
Does your TV have headphone socket, and if so what size of output jack? How does your TV get its signal, antenna or what?
If there is no headphone jack on your TV you are still out of luck. Your only solution than is buy an old VCR and drive your TV from the VCR. You then use the VCR as the tuner and connect the audio outs to an audio input on your ONN.
Your other option is to subscribe to SKY TV and use the Sky Box audio output.
The other issue is that Onn unit is a fraud. It only has multichannel analog audio ins. The problem is that a lot of gear now has only digital bit stream and pcm outputs. So if you use the VCR you will have to use your Dolby plx 2 input. That will give you matrixed surround, not true surround. It will be the same for a Sky box as they only have stereo analog outputs. The audio multichannel out is optical. It also has HDMI out which sends audio and video in the same cable. There are different models of Sky Box, and not all have surround and HDMI etc. You have to make sure you order the right one.
If you can return that Onn unit, return it, get your money and run. Then put your money towards an AVR with a modern selection of inputs and outputs, including HDMI. Then you can also get a decent set of speakers.