for English, there is no correct accent.

If you learn UK British English you will likely be taught, southern or Oxford English Pronunciation.

From the teachers speaking not from a book.

You will most likely be taught Cambridge English following Cambridge University course books.

If you come to The UK it will take another two years to get used to the hundreds of accents in the UK, it will seem like you learned a foreign language In the classroom. This is something I have heard many visitors complain about and be shocked by.

Please check this book https://youtu.be/_1sEg_aWbJ0 ;

You may also find pdf of the book here http://www.alleng.ru/d/engl_en/eng073.htm