追記です

maddycatさんの紹介している

http://www.tickets.london2012.com/howtobuy.html

は、

Authorised website

London 2012 is the official ticketing site for visitors from the UK and designated European countries
The official ticketing site for residents of the UK and designated European countries is www.tickets.london2012.com

Individuals from outside the UK and designated European countries should see our list of official suppliers

と、戻ってきますので、ご安心を。