Пажалуйста, надо подготовиться.

   Dear (имя друга),
Hi! Thanks for your letter invitation. 

  Well, when should I go to Britain? In June or in July? I know that the most attractive places in Britain are the Tower of London, Stonehenge, Big Ben, the London Eye, Buckingham palace and others. I would like to visit the Tower of London because it's one of the most famous places in Great Britain and I know many interesting facts about it.

So, I need to go now. Write soon.
Best wishes,
Своё имя.