Just been reading over on the Virgin Media forums, about some TVs not being able to handle the UHD/HLG. Seemingly mine is one of those, Sony XD93, but it handles the Planet Earth 2 HLG trial it auto switches to HDR mode just fine. And I've watched one or two 4k HDR Blu-Rays on this tele and all works as it should. Yet the options to choose UHD etc don't show up on the iplayer for me either through the V6 or the TV. Very strange.
The only possible thing I can think of is I need a different HDMI cable the one's I have are about 8 years old and not up to 18Gbps spec. Although they work perfectly fine on the PE trial and those Blu-rays. I have some syncwire 18Gbps HDMI cables arriving tomorrow so I'll see if that works. If it doesn't, I'm out of ideas. Regardless the HD picture on good old BBC1 HD is great though.