Thats normal for O2. Their systems are pre-historic.That doesn’t sound great. Hopefully though it’s just a glitch and you’ll get it in the original time frame that they promised.
They send emails like that because their system shows its not available to ship at the moment you placed your order. It doesnt understand the concept of a pre-order.
It not unusual to be unable to find any trace of your order on your online account with them until its shipped either.
They can also be really, really late sending out shipping confirmations. I've gone to bed in the past not expecting my device to arrive on launch day, and the shipping email has arrived in the middle of the night for delivery that morning.
Its rubbish, but not a cause for concern.