Examine Shopify cart for product vendor to customise

I'm hoping for some help with liquid in Shopify, I'm having trouble with trying to customise the cart based on what product the customer has added.

Basically if a customer adds product from Vendor A then I want the cart to load the template to customise the cart for Vendor A

But if product is from Vendor B then I want it to load the template to customise the cart for Vendor B

But if the cart has products from neither (or both) then I want it to load the default cart.

I started down the road of conditionally loading snippets based on product.vendor but I couldn't that to work for some reason and maybe that's not the most efficient way anyway.

Any help massively appreciated!