假如你是李华，你的英国网友Peter想作为一名交换生来你们学校学习，请你根据要点提示给他写封e-mail，介绍

Dear Tracy,
I feel sad at your going back home.You know I am very happy to enjoy the time you stay here.You've been always very kind to me.You have helped me a lot on my English study.I hope you can stay here longer but I know you also miss your hometown very much,you must be very keen to see your parents again.I know they are missing you,too.And if possible,we be together again for you can come back some time later,after you've finished what you need to do.So good luck to you,Have a good travel back to UK.