Thanks for asking.
You'll need to be there for 7.45pm; allow 20 - 25 minutes to get there, and ask your taxi driver to pick you up again at 9pm.
Is this between June and August?
In which case I would suggest getting there for say 7 - 7.30pm and you'll be able to use your confirmation letter to get into the exhibition centre before it closes, have a look at the gift shop, and have refreshments (if they haven't cleared it all away) before the site closes at 8pm. (and then you'll have your inner circle visit)