Hi Monikapop, I would be inclined to sorce your own HDMI cable just to satisfy yourself, it won't be the first time virgin have maybe supplied the wrong thing, they don't cost a lot of money.Regards Micky
Just checked a few things from over here and your signal levels seem to be fine going into your TV box. Can you confirm that the pixelation issue is happening on all boxes in the home? (If you have more than one).
In regards to the WiFi issue, does this affect all devices in the home? Your speeds seem to be fine coming into the property as you say you're getting round the 500mb/s mark near the router. I'd recommend having a quick look at our WiFi Wins forum post to ensure that your wireless set up in the home is good.