[Theme: Evolve] – Header & Menu Overlapping

Hi. I am running the Evolve theme on my site https://www.doyouwoo.com

Originally I just had Title & Tagline in the Header (as per the General Settings). Feeling somewhat ambitious, I have just created a header with 990px x 170px as per the theme guidelines, and uploaded it via Appearance/Header.

Then when I reload the homepage, the top menu is now covering about two-thirds of the header. This did not happen when I didn’t have a custom header and just used Title/tagline – the menu was directly below the header then and looked fine.

I don’t know if this is as simple as some box I’ve neglected to tick somewhere, or a known issue with Evolve.

Any ideas? I’ve left the messed-up looking header/menu on the site btw so you can see what I mean!

Thanks for any help,
Chris