Ok so an update:
Last night I left music playing while I went to sleep (managed to turn it on by using the flashlight through the apple sign trick). Then this morning when I woke up everything seems to be working fine again?! So the backlight for the screen is fine (right now at least), and the keyboard too? Could this have been some kind of software issue? Or do you guys think I should still contact the repairer in case it happens again/is it likely to be a recurring issue?
Thanks for all your awesome answers thus far!!!