If you're interested in attending an English-speaking church service I recommend that you go to the following website which offers English speaking services in central Barcelona.
Several site visitors have asked me about churches that are English-speaking and for a specific denomination. On this point, I recommend that you send an e-mail message to the English-speaking church and ask them directly. They are likely to know of other churches that may be able to offer the service that you are looking for.
And if you do find a church for a specific denomination, feel free to send me a message and let me know the details so that I can post it up on this site.