Thanks for the reply Dasius.
Because I'm stubborn I tried to figure it out myself and it turns out you can bind the cursor keys, but they are somehow also pre-bound to menu navigation so attempting to input them as bindings is difficult as the often the key presses navigate away from selection field before it registers the Key change. I noticed this as while attempting to bind the cursors I noticed a faint highlight box would appear around the sandbox mode button.
I guess this should be in bug reports then...