Inge - ask to speak to someone in charge, a supervisor or a manager, then tell them you are going to be in England and to please have the tickets sent to the box office and NOT posted to you in Germany.

I called them today on behalf of Nath (from France) and they said her ticket will be at the box office. You will need your credit card that you used to book the tickets, your passport and your confirmation number.
If you booked them using someone else's credit card, you will need a letter of authorisation from that person.
The box office will be at gate called "Elizabeth" and will open at 2 PM!

I hope this helps you and others.

see you in London!!!