I have created an epub 3 with full screen background video and buttons and text on top, this works perfectly on my mac in ibooks, but wen viewed on an ipad or iphone, the video opens up in a video window automatically and thus ruins my overlay effect, can anyone help or explain the best way to get round this?
I've moved your question to the InDesign EPUB forum.
I think you're out of luck. That's not the way EPUB readers work. Each chooses its own way of displaying videos. I'm not aware of any way to change the UI the way you want.