I realize this isn't what you want to hear but you will need to disable the ad-blocker to get the video to work on sites such as Channel 4, ITV, etc.
I think it may have something to do with the adverts they play inside the video player.
I've had to whitelist both C4 and ITV to get them to work.
Aside from the "AdAway workaround" - I am really confused that nobody dislikes all the advertisements in Opera now.
The last version used to be ad-free, plain, content-focused - and now this? Speed Dial / News has ads every where, reading mode has an ads on the bottom - this should not happen when the ad blocker is enabled.
I would even pay for an ad-free version - how about that, Opera?