Okay so... This update helps with the UI. All I've really done is added a Pause Menu to each of the levels.
To access this Pause Menu you just need to press Start on an XBox controller or the Esc key. I personally use a terrible Logitech controller with my Mac (for some reason my xbox controller doesn't play nice with my mac), and it has a couple more keys, so the "Back" key works instead of the "Start" key, so just bear that in mind if you're using third party peripherals.
I haven't yet integrated any sort of menu controls with the controller, still just using standard UI buttons, but at least you can pause with the controller if you get stuck.
Oh! And if you just press the Start button from the Main Menu, it starts the game. That way you don't have to put down your controller once you start the game.
There was a lot of stuff under the hood that went into this one too, a few optimising tricks I really should have just done to start with, but apparently I had a brain fart.