Hi, thanks so much for this suggestion. It is so close to delivering what we need but there were a couple of issues.
If you see the below images it shows what it looks like when you first log in and then once the video is playing.
It has successfully altered the size of the video, which is what we wanted. However, it shows the image of the channel owner, the YouTube icon and has a black border around it. Is there anything that can be done on those points please? Thanks for your help!