Thanks, had been checking every few days. Notice the "It's still not live" bit is still on the website, although that's probably to stop lots and lots of people trying each time.
I just moved mine forward 10 days (to the day after giving blood). Also Old at 45.
You can now book boosters for 3 months after your second jab, and make the appointment 2 months after.
I've just moved mine forward by 8 days. Now the day before the office party. Hmmm...