No, there isn't. And I think that's wonderful and one of the sources of English's strength and beauty. English dictionaries and textbooks are a kind of "free market" operation. Certain dictionaries have won positions as respected authorities (Oxford for British English, Merriam-Webster for U.S. English). However, the tradition in English is that dictionaries are "descriptive, not proscriptive." They describe the language as it is. They do not proscribe, that is to say lay down rules, for what they think it should be. I once won an argument with my tenth-grade English teacher... in 1960... about Merriam-Webster's Webster’s New International Dictionary (_second_ edition). He said the pronunciation listed first was the "preferred pronunciation." I raised my hand and said "No, it's only the most frequently used pronunciation. It says so in the introduction." My teacher glared at me. Then he walked over to the dictionary, opened it, and looked at the introduction, looked at the class, and said "he's right."

No such group exists for English. The closest thing is the Oxford Dictionary (https://en.oxforddictionaries.com/), although that records English as it is used, rather than creating rules about spelling and grammar.

Not a group as such, but you can look to standard dictionaries (eg. Oxford, Merriam-Webster, Macquarie) for word usage in different English-speaking countries. Naturally, being dictionaries, they tend to report on the current status instead of telling us how we should spell words. You can also look at the "style guides" of different countries and regions, as these outline how English should be presented in a standard publication.