Hi Nick
Have you connected the soundbar using the eARC HDMI socket on your LG TV and then added it via the Universal Control Settings on your LGTV ? I was able to type in Ultimea as the device manufacturer on my LG TV and it found a match. If so then providing you have Simplink (HDMI-CEC) turned on on your LGTV and One Power turned on in the 360 settings then you should be able to control the volume using the 360 remote if you have the Volume keys setting showing under Audio & Video.
You might also be able to control the Ultimea and the TV360 using your LG Smart remote? I'm assuming you have an LG Smart remote as you haven't said which model of LG you have.
I have a couple of LG TV's and have set them up to control my 360.
Some TV's recognise the box as Virgin, with others you may need to search for Ziggo, or Ziggo Mediabox Next
On both of mine I went via the Universal Control Settings. It shows Virgin (North East) and View More. If I click on View More and then Next I am shown a list Set-Top box providers ( Sky, VM and BT)
If I move cursor up I can place it in the Search box then click OK and type in Ziggo and press Enter.
It then brings up another screen with Ziggo highlighted. I then click on Next and a new screen appears, 'Remote Control Operation Test' I press OK again and the main VM channel that's playing appears in a mini screen, along with a highlighted PR⬆ - I then press the OK button and highlight either Yes or No onscreen (it doesn't work first time for me) but the second time I click on PR⬆ it changes channels so I click Yes to show it's paired, and then Done.
Once the LGTV remote is paired with the 360 you can bring up additional options for the 360 by pressing the context key (above the channel up/down keys) on the LG remote.