This them is very anxious for me because I'm currently learning the English language. There are many English teachers, who think that only a British version of English is correct, every other accent is wrong and this is not true English language. And as I know, a lot of British people thinks that TV channels should make a translation from US English to GB English. In this article, I will write what I think about this.
Yes, it is a fact, that English language coming from England (it is obviously). And each other country, where English is the main language was colonies of Great Britan in the past. But it is not true that if the language was born in the country, then every native speaker from this country uses the correct form of this language.
There are dozens of versions of English in the world (US, Canadian, Australian, South African, New Zeland, etc.). You even can find them in the language settings of windows. And they are different, they sound different, some words and meanings are different. Even in limits of one country exists different accents of local English (like in the US you can find NY accent, Southern accent, etc.). And people that live in Scotland, for example, could don't understand some guy from Texas.
In my opinion, the most correct form of language (accent) is the accent, that is more understandable and clear (because the language is first of all not grammar rules or high score on the test, it is verbal communications between people), even for non-native speakers, like me. And most part of Great Britan's accents is very difficult for understanding (even for native speakers, like one Australian guy that I know said).
For example cockney accent, this accent even was created for encrypting what you talking about (cockney were used by criminals in the first years after establishing). All these Liverpool, Welsh, Scotish, Irish, West country, etc. accents are very different between each other. Some of them sound even like other languages (especially Irish accent). I even not sure if people that live in different parts of GB can clearly understand each other.
Yes, Received Pronunciation (RP) English is very easy to understand, but you can find it only watching BBC programs and listening to some GB radio stations. Almost no one uses this type of English. The most understandable type of English pronunciation that uses many people (more than 100 million) are accents from the US. Yes, there is some marginal part of the country, that speaks on very specific and difficult accent, but most part of Americans uses very simple for understanding, and (as I can tell from my own practice) for speaking.