Not every video has a stream to start with, according to cute, and those that have, seams to be playable at most when downloaded as 360p MP4 audio/video.
720p MP4 audio/video starts playback of both audio and video, but cuts out pretty much straight away, (something like a second plays) with the error saying it's not a compatible format. Ignoring the message and pressing the "play" icon again plays the next second, and so on. I'm guessing i need a better player then the default one at this point.
Neat that downloading works, i didn't even know that was a feature. Thanks.
B!