i rang the ticket office around 2pm yesterday, explained my tickets hadn't arrived.You should have received a email from Wembley yesterday to print off your tickerts
i got an email with a pdf at around 5pm, printed them off today :)
In response to zabbas_dad - i booked my tickets on Wed, rang the ticket office / City supporters.
But yes, as above, can confirm that the guy at City Supporter's help line said that if tickets didn't arrive on time, or you were unable to print them, there is a crew at the Wembley box office who can print them :)