Thanks for all the advice - heres an update to my initial post.
I went and purchased a Samsung HW-S50A which was relatively cheap compared to some soundbars and is the same brand as my TV - it has optical, bluetooth and HDMI so I was happy to have all options covered.
My V6 box is connected to the TV using an HDMI cable (of course) and I connected the soundbar HDMI port to the TV eARC HDMI port using a second HDMI cable.
I know many will already know this but... When I turn on the TV using the V6 remote, the soundbar comes on, switch off TV and the soundbar switches off - I think this interaction is a standard feature of the eARC hdmi connection. The V6 remote also controls the volume of the soundbar so its a really simple setup. The soundbar has its own remote to control some of the settings but for many it wont be required day-to-day.
Sound - an immediate and incredible difference and I don't know why I haven't bought one before! There are lots of settings and room settings for me to play with (which I may do over the weekend) but out of the box the sound is just miles better and by 'better' I mean I can now hear whats going on without regular rewinds or even subtitles.
You've got the correct connections. As your soundbar supports 3.0 I suggest that you set your box's audio to Dolby Digital (for V6) or PCM 5.1 (for 360). I'm hoping that your TV will send through the audio as received from its HDMI cable (as it's HDMI eARC).