Once you visit Barcelona (and Andorra), you'll know about Catalunya and the Catalan language, but there's no need to translate. There is a group of flags at the top of the home page of the website you're using. If you click on the British flag, presto! English!

As far as the credit card denials, you may need to advise your credit card company to expect charges from Spain and Andorra.

I think there are multiple companies operating buses from BCN.