I'm having these problems too on my lg oled. It has definitely got worse recently to the point where I started watching a programme I'd recorded on the v6 box on bbc 4 and the picture was that bad I thought I'd set it to record on sd. I ended up watching it through the iplayer app on the TV for a much better picture. Don't get me started on sports either that takes the problem to a whole new level. Have virgin even acknowledged there is a problem yet?
I too am having the same trouble. I'm using an lg OLED55BX6LB and the picture quality is terrible across all the sky channels. There is a massive difference between bt, bbc, itv sport coverage compared to the sky offering. I've tried changing all the video outputs on the box and tweaking settings on my tv but nothing makes a difference. For the price I'm paying each month I expect far better.