I entered the BusyBox console from the 'Select Language' screen using using Alt + F2 and now I want to return to the install process. If I type 'exit' I can get back to 'Please press Enter to activate this console.' but if I press 'Alt + F2' nothing happens. I have also tried with Ctrl and Ctrl + Alt F6.
The reason for all this is I am trying to install Ubuntu Server 14.04 on a Dell R410 using a USB stick but, for some reason, the installer gets stuck trying to load files off a CD drive that doesn't exist. To try and fix this I am following the instructions in this answer: https://askubuntu.com/a/130826