Improve basic styling

[mlewis-everley]

At the moment the base theme is a little clunky. I think we need to improve it a little. It still needs to be a simple basic theme that can be easily styled to make it look different, but it should also be a theme that we can use largely unedited as well.

Some possible ideas o take inspiration from:

• https://themeforest.net/item/shum-ecommerce-html-template/24552685
• https://themeforest.net/item/comero-ecommerce-html-template/24226484
• https://themeforest.net/item/munmart-minimal-ecommerce-html-template/24495082
• https://themeforest.net/item/smarttech-ecommerce-html-template/20756752