One possible version：

Dear Cheng Wei,

I’m very glad to know that you will get a chance to study in London for a year. I’d like to tell you something about London so that you can have some ideas about it before you come.

London is certainly one of the most famous cities in the world and the school which you are to attend is also well known. I am sure that you will improve your English quickly here by communicating with teachers and students here.

After you come to London, you will live with a host family, which is a good way to help you learn more about the local customs and the English people’s way of life. During your spare time, you can go to visit the places of interest in London, such as Big Ben, the River Thames and the London Eye.

Of course, there are some disadvantages living in London, for example, traveling, at times, can be difficult, particularly by car. Despite these things, I am sure you will have a good time staying and studying in London.

Looking forward to your coming.

Yours,

Jack

题目分析：写作前要仔细审题，根据要求可知这是Jack写给程威的一封邮件，包括四个方面内容，写作时不要遗漏要点，但同时还要注意要点表述的条理性和层次性。其次要使用一些连接词以使文章内容连贯，上下文衔接自然。此外电子邮件虽然不像书信那么正式，但是要注意语言简洁自然，主题突出。最后在时态方面，因为内容涉及到将来，所以在介绍情况时可以使用一般现在时和一般将来时态。

【亮点说明】本文要点全面，语言流畅。作者在信的开头，开宗明义提出写信目的的同时也表示了由衷的祝贺与欢迎，语言亲切自然。在结构上分段介绍学校、住宿方面的便利和优势以及一些不便之处，这样的段落安排使文章结构分明，层次清晰。其次，作者使用了很多涵盖信息量较大的复合句，如宾语从句that you will get a chance to study in London for a year，目的状语从句so that you can have some ideas about it before you come.定语从句 which you are to attend is also well known等。此外，During your spare time 、such as Big Ben、Of course、 for example、 Despite these things等大量短语的出现也使文章内容衔接更加自然，语言更加连贯。