Whether you are studying English in London or studying English online, one thing that can really help your progress is using English regularly. Students often feel frustrated because they find that they are always translating in their head before they speak, and speaking English frequently is a way of forming connections in your brain that will make the language come more naturally.
One huge myth about learning English is that by speaking to non-native speakers, your language will get worse. This is not the case. Using English regularly improves both your speaking and listening, and can move words from your passive vocabulary. In addition, the majority of conversations that happen in English are between two non-native speakers, so it is good practice for future work situations.
If you are learning English in London, it is easy to find other people who want to speak English with you, because English is the main language of the UK. Going to shops, interacting with other people, and listening to people talk in public places all improve your listening and speaking,
However, students have told me in the past that they struggle while in London to make British friends, and most of the time, this is because they are not going about finding them the right way. There are, however, a number of ways in which one can make British friends, which hopefully will seem obvious once you have read them.
Firstly, students in London often go out to bars or clubs in the most touristy areas of London and then complain that they only meet tourists. Do some research online and find cooler areas to go to. Often these will be outside zone 1 (the centre of London). It is also important that you want to go to these places. It is unlikely someone will want to be your friend purely on the basis that you wish to practise your English. Find bars or clubs that play the type of music you like and you may be able to form a bond with someone over that music.
Secondly, if you are interested in sport, joining a sports club will involve communicating in English with other people. Or if you like reading, join a book group. Essentially, joining some kind of hobby group will give people a reason to connect with you, providing lost of future opportunities for you to practise your English.
If you think about your friends in the country you come from, you will hopefully find that none of them became your friends simply because you wanted to practise talking with them. The friends you make in London should not be any different!