I don't know of any English-speaking country that has a government-issued standard procedure for pronunciation. However, the most commonly-used standard is, if I am not mistaken, the Oxford English Dictionary. It details proper British English pronunciation, which itself has many dialects. American English is, in my opinion, a bit easier to grasp (America has only existed for a little over 230 years as opposed to England's 1000+, after all, not to mention other kingdoms nearby such as Scotland) in terms of pronunciation and vocabulary.
I think the reason that America has less dramatic variation in dialect is that the United States only existed for about 120 years before the invention of radio, and 170 before the invention of television. Mass media and communication creates a larger community, and tends to prevent or eliminate language barriers over time. Not to mention that nations with longer histories have been conquered time and again, which creates a culture shift every single time that happens.
Sorry for the tangent; I enjoy history.