Dear xxx(不知道他的名字.)
Hi,my name is XXX(你名字) and I come from China.It's a nice chance to write letter to you.
I know that u r from London,UK.It is one of my favourite city and in my memory,it is a city with variable characters.It's really a attractive city to me,I wish I can visit there in the future :-)
Look forward to hearing from you,I would love to know something about yourself
Best regards
XXX(你名字)