During the night my TV box turns itself on and starts up the TV, which is very annoying as it wakes me up. I turn off the TV using the blue button at the top of the remote control and the TV box with the red button next to the blue button.
If the TV is turning itself on in the middle of the night when connected to the YouView box, this is usually when the TV box shows activity, such as a software update. This is caused because the TV will have HDMI CEC active.
This is Consumer Electronic Control (CEC). This is a feature of newer TV’s to allow them to to see the devices connected and to control other devices. You can look through the TV menus and there will be an option to turn HDMI CEC off or there will be 1 HDMI port that will not have this feature.
Mine changes inputs when it does it's nightly update, even if I am watching something else on my Humax box, NOW TV box or Blu-ray player. I have reported it on here, to the trials team and to Youview directly.
As Karl says, when it updates even if the box is in "DEEP SLEEP" it sends a pulse through the system, including to the TV causing the trigger to your TV.
This is the only option I'm aware of that can potentially resolve the issue. Did you check to see if there are other HDMI ports on the TV that are not controlled this way ?