It seems that Edexcel holds four exam sessions: January, March, June and November. The deadline for the registration of the November session, according to the Edexcel website, in
2010 was 4th of October 2010. The documentation for the sessions spanning over November 2011, January 2012, March 2012 and June 2012 has not been released as of yet. I checked this information on
this website and the document I referred to was
Key Dates. However, I exhort that if you are appearing in your exams via any kind of school, academy or organization, please get in direct contact with them because application procedures and deadlines may vary. If not, try to get in contact with a friend in your locality who can get this information from his/her institute.