Theme Advice with CSS Support

Hi All, I’m new to wordpress but with a little help from the experts on here I think I can achieve what I need to.

I have been looking around for a theme that matches the one on https://www.thenottinghamshire.com/ I particular like the idea of the 4 images that link to various parts of the site, what is confusing me is how have they called the sidebar because I see no reference to get header in the index,php and from within the CSS style sheet either nor do I see a reference to get sidebar.

Which theme would best suit me to get started with the creation of my first wordpress site so I can try and emulate the above site

Thanks all

Martyn