People don't expect you to speak a language perfectly if it's not your native language, so don't hold yourself to those impossible expectations. As long as you put in effort, people will be willing to help you through and put in effort to understand what you are saying. Embrace every mistake as an opportunity to learn more and you will keep improving :) Best of luck to you :)

Your answer is in your question. The English people are friendly., so don't be afraid of saying something wrong. They will think more of you, not less, for speaking their language. Also, don't be afraid to ask for help. If you are confused and are near someone who looks friendly, explain to them what you are trying to say, in whatever words you know. Doubting our own knowledge in a foreign language is something we all do. Don't worry about it. Finally, you have taken the biggest step toward learning English. You are in England. Be happy!

Thank you, Leonid!

Hmmm.. i mean learn the language ;-)

Don't be afraid, just relax. You can't teach the language without the mistakes. It is normal to make mistakes. But you still need to dismiss the mistakes.