For some reason after the first time I restarted Yakuake seems to be absolutely dead... The F12 key now only seems to select and deselect my current application. I have tried reinstalling it from the software center, I've tried using terminal to open it and only get the message "Yakuake is already running, toggling window ..." but nothing happens. I have literally done nothing other than restart my machine and this is broken. I had Yakuake set to start on login and it's worked perfectly for ages. I am usually pretty good at sorting this stuff out myself, but I am afraid that I am at a loss...someone please help.
The following 'answer' was posted by the OP of this question:
Turns out I'm a complete and utter moron and Yakuake is in fact working, but I am using a laptop connected to an external monitor and have extended desktop on. I had already set yakuake to open on my external monitor, but somehow that setting had changed and it was opening on my laptop, which was closed because I had forgotten I was using extended desktop. Excuse my stupidity, I'm going to go cry a little at my own stupidity now. Thanks again folks.