Well, doesn't matter how much I planned, I couldn't emulate traffic hitting the website.
The server ran into a problem with a process hanging which brought down the server. This caused downtime between 5:00-5:30. I hope you can understand this server has been recreated from scratch, almost everything is different.
I'm having this investigated now to prevent this happening again.
I thought the downtime might be due to the new set-up. Thanks though for explaining things so clearly - at least as far as I need to understand them.