Space above sticky header on York!

Hi there!

I've put a Sticky header into a site built on York, and it works perfectly on the index pages, but on the Contact, About and Press pages, there's a big gap above the Nav Bar. I want the coloured Nav bar to remain glued to the top of the screen as it is on the Index Page.

What's wrong with this code? It's bits I've grabbed offline and put into the custom CSS section. I don't know how to code so it's total guesswork and any help would be hugely appreciated. I've attached a screengrab of the index, where the navbar sits at the very top of the screen how I want, and the about, which has the horrid gap.

#header { 
   position:fixed; 
   z-index: 1;
   background-color: #402C30;
   padding-top: 13px;
   width: 100%;
   padding-bottom: 13px;
   margin-top: 0px;
 }

@media only screen and (min-width: 760px) {
   .site-page {
       padding-top: 40px !important;
   }
}

still no luck!

Can you share link?