I understand will be able to fix this with the addition of:

params.wmode = "opaque";

towards the expensive element, but however , this really is on the Wordpress blog where every (over 250) publish includes a expensive video baked into it and so i can't really alter the code for every publish. Can there be anyway either to change all of them instantly using using jquery or something like that, or perhaps is there some method of doing this using CSS?

The Wordpress site under consideration is Sometimesdaily.com. You can observe this happening should you click the videos to see a "single publish" page, then hover within the "Video" link around the menu bar.