Some pages on site not full secure

Hi, I've got a site with an SSL certificate which, on the whole, works fine but there are a few random pages which show as not fully secure (they say https in the URL bar but with some warnings). Any ideas why?

The main site is http://www.church-supplies.co.uk

The random pages are...
https://www.church-supplies.co.uk/how-to-order/
https://www.church-supplies.co.uk/delivery/
https://www.church-supplies.co.uk/money-back-guarantee/
https://www.church-supplies.co.uk/wood-finishes/

It's possible there are others but most of the others are in the WooCommerce structure and I'm pretty sure they're all fine.