Originally Posted by Mustang Sally
Thanks! (Who knew I'd be so fondly remembered...)
To the subject at hand, I've just disovered you can even upgrade some 48 hours in advance if you get a friendly booking agent on the SE number!
...and if you do this, you may well find yourself being asked for an upgrade certificate at the airport. SE agents should not be processing online upgrades in this way, so you may just be being put into I class and will be asked (correctly) for a certificate.