Show sticky header only on scrolling

Hi, I have found code to get rid of the header on a page successfully but would actually like it to appear as the visitor scrolls, say past 500px down the page. 

The idea is to have a full screen landing page for the site with the logo centre page and then when this is scrolled passed the header (which will also have the logo in) will appear withe the navigational elements. It will avoid the site having 2 logos present on the landing page. 

Many thanks for any assistance.

My site has no real structure or content yet so I didn't give the URL, as this is the first task to get right.

Graeme     

Can you share site url? We can check easier

Thanks for getting back to me, I think I've solved it. If not I'll pop the site here when there's something to look at. 

Best,

Graeme