Who is an English learner who doesn't dream of coming to the UK and speaking like a real Englishman? The famous Russian accent is easily identified, but it is quite possible to defeat it, you just need to work hard on it.
Listen and talk
It is quite possible to learn how to imitate a British accent, but you need to know how it sounds. You should watch English films as often as possible, listen to audiobooks and lessons read by native English speakers. Stephen Fry, a renowned English comedian and writer, is considered a native speaker of the "perfect" British English language and has recorded several audiobooks that can be a great resource for a language learner.
There are many accents in Britain that differ from one another. Going to this country, you may be surprised that the British themselves do not always understand each other well. For example, residents of London are not always able to easily make out what the residents of Liverpool want to tell them.
You can fully understand the British accent only by listening to the speakers' speech, and mastering it only by repeating after them.
The salient features of a British accent
One of the main features of the British accent is the pronunciation of the letter R. When it comes after a vowel, drag and then add something like uh at the end. So, instead of the word here, the British get something like heeuh, and the word hurry sounds like huh-ree. Another feature: words ending in rl or rel are always pronounced with a reduced R.
The pronunciation of the letter U has characteristic features; it is not spoken as O, but as ew or you. For example, the word stupid sounds like stewpid, but not stoopid.
The letter A often sounds like Arh or Ah. So, the words bath, grass sound something like bawth, grawss.
A very characteristic difference between American English and British is how to pronounce the letter T. The British skip it, or it sounds very soft, and Americans often replace it with almost D. Where this letter is present, it seems like a small pause in British English … This is also called a hard attack.
Words like been are pronounced bean in Britain and bin in America. The short version can be heard rarely, only when the word is unstressed.
Listen to the tonality of the language. The British accent is largely in the intonation, tone and emphasis of speech. Please note that the end of the utterance may end with a rise in tone, and not a decrease, as in Russian.
It is best if you ask people from different regions of the country to say a few simple phrases. If this is not possible, you can search for videos in which the owners of different accents participate. It's good if you can see how they pronounce the words: whether they round their lips, open their mouths, and so on.