Modify the checkout button text in the cart and remove tax from the order summary section

https://dragonplanters.co.uk/cart

Password for the site is : dragonplanters

I need to modify the checkout button to include the text "checkout ( excludes delivery)" from the link https://dragonplanters.co.uk/cart. Please make sure you have added some products to the cart to see the checkout button. Also, I need to remove the tax title and the £0.00 following that on the checkout page. Is this possible? 

I am doing this because I have included 20% VAT in the product prices and delivery prices already and do not want it to be shown seperately at checkout.  

Would be great help. Thanks!  

@paul2009 That's great. thanks!
Is there a way to add a text box on the page https://dragonplanters.co.uk/cart where the text says  " If you want to order a combination of different types of planters, then please contact us for the best delivery options." 
I need the text to be situated below the checkout  button and it can simply be text. It does not need to be in a text box. I might need to add some other text over there in the future. 

I have created a quick guide for adding text here: 

Adding Text to the Squarespace Cart Page. 

Let me know what you think. I would recommend adding a cart message just above the checkout button, as it is more likely to be seen there, but I've added guidance for below the button too!