Hi Justin
Thanks so much for your quick reply.Unfortunately I did try defining hight and width as 100%, but this did not work.
I've also tried both the CSS method and JS in the link you provided and I can't seem to get this to work either...With the CSS and JS code am I meant to be attaching this in the resources section of the export? Or should it be embedded in the back end of my webserver?
I tried the CSS method with this attached as a resource:
.video-container {
    position: relative;
    padding-bottom: 56.25%;
    padding-top: 30px;
    height: 0;
    overflow: hidden;
}
.video-container iframe,  
.video-container object,  
.video-container embed {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}
And this is what I pasted in the iframe indesign:
<div class="video-container">
    <iframe src="
https://www.youtube.com/embed/8ekR-Wid7V0" width="800" height="450" frameborder="0"></iframe>
</div>
i've managed to get embedded media file videos working, but not any youtube/vimeo videos....Any suggestions on where I'm going wrong?
Thanks again!