Removing the Marquee blog page header?

I really need to remove the header entirely from my blog page, using the Marquee template.

Does anyone know of anything I can add to the CSS to remove this header? I used this code to remove the header from pages in the Index (the homepage one) where I had not added a thumbnail and it worked in removing the header but it doesn't work on the blog page:

<style>
.title-desc-wrapper.over-image {
  display: none !important;
}
.title-desc-wrapper.over-image.has-main-image {
  display: block !important;
}
</style>

Or does anyone have something entirely different?

This is really urgent so any help would be very much appreciated.