For those of you who have signed up for Elite but never got your initial double xp for signing up here is what you can do.
1st. Go to your profile and unlink your Gamertag from your elite account (@elite.callofduty.com)
2nd. Sign out and then sign up for a new account at elite.callofduty.com using a different email address.
3rd. Once you have signed up with the new email address go to your profile, and then re link your xbox live account.
Following the above steps should ensure that you receive the outstanding double xp. It is a lot of hassle to go to I know but I have seen a few people who are having trouble getting their initial double xp for signing up to elite and for those who desperately want the double xp this is the best route to follow. This Information was given to me by Activision Twitter Support, and it worked for me first time, so hopefully it will help some of you guy's.