I've managed to bring all sites back up now. The problem was caused by matching the domain name to the website account, for some sites (seems to be quite a few of you) this broke down.
This only happened to a handful of websites hence why the monitoring didn't fire, which prolonged the fix. I have added additional monitoring checks so downtime will be detected in the future.
I will continue to monitor during the next few hours to ensure everything runs to working order.