Reduce Height WooCommerce Storefront Headers

Hey All,

I’m really, really new to all this. I’m using a child theme of WooCommerce Shopfront at http://www.otherworldbooks.co.uk but at the moment the header / navigation menu / title is taking up most of the screen. I’d like to neaten it up to reduce the big blank gap between the page menu under the header and the page title, but I’m not even sure what attributes are governing this! None of the CSS code I’ve found relating to changing header size seems to make a difference, either through Jetpack or input into the CSS, and in fairness it’s only the height or gapping I need to adjust, not width etc.

Hope someone can help!
Thanks,
mindorra