Changing/Getting rid of Zip Code box in the basket

[guesswhatiforgot]

You might have to pop something in the basket for it to show.

 

http://pamperyourpet.co.uk/order or here is a screenshot http://puu.sh/8WlsQ.png

 

I want to either get rid of, or change the wording of "Zip Code [           ] (needed for certain carriers)

 

I've looked and looked but can't find the right file.

 

Does anyone know what the file is called?

 

Thanks in advance