Hello,my dear friend! (Или имя друга)
How are you? I have a good news: I'm going to go to London on 3 days! I always dreamt about seeing this nice city. I want to visit Big Ban( now it's called Elizabeth's Tower), The House Of Parliament,Buckhingham Palace and others beautiful sights of the capital of England. Could you help me with this? It will be amazing ,if you agree. I'll be very grateful to you for your help. By the way,how is the weather in London? I need to know what clothes to take with me. Write me back as soon as you can,I'll be waiting for your answer! See you soon!
Best wishes,(твоё имя)!