AND FINALLY A SOLUTION!!!
I hope this helps everyone else that's been in this battle of an issue.
When connecting the airpods to the TV, they have a built in volume which is disconnected to the TV volume, and this defaults itself to minimum hence seeming like there's no sound coming through.
If you use the new airpods, and using the side of them increase the airpod volume directly (stroking the stem upwards) you will solve the problem! It's the point that the airpods volume was set to the bottom when connecting and hence we thought it was an issue with the TV, but it's not!
Hope this stops anyone else from spending countless hours searching / troubleshooting the TV connections. I imagine this applies to all smart TVs, beyond just the LG / Samsung experiences I've had.
Volume control process on airpods: Pause, skip and adjust volume with your AirPods and AirPods Pro – Apple Support (UK)