Css sidebar help please

Hi, I have quite heavily modified the twenty fourteen theme to meet my friends need, but I am having issues with the side bar. I can not get to to be the full length of the page, any help would be greatly appreciated. and example page would be:

https://trevorjonesltd.co.uk/shop/product-category/brass-accessories/

If you browse through the the wordpress part of the site, you can see this issue is on every page which has content longer than the side bar.

Thanks