From the official site:
Selling Arrangements
Tickets will be available from the Ticket Office from Wednesday 23 July 2003, during normal office hours, Monday - Friday 9.15 am to 4.45 pm, for as long as supplies last.
Telephone Credit Card Bookings
Credit card bookings will be available from Wednesday 23 July, telephone number 0870 220 2151 and will be subject to normal booking fees.
Postal Applications
Postal applications can be made to the Ticket Office, subject to availability, enclosing the correct remittance and a stamped addressed envelope.