That means one side is working and the other is out. Once you're at it, it's best to change both bulbs, as if one gave up, the other one may soon follow. And as for the fuses - there're normally few things on each fuse, so if you'd loose say stereo, electric mirrors.and backlight, that's telling you there's a fuse. Some items have dedicated fuses on their own, but such low amperage items like backlight will always share fuse with other devices on the car. Hope this helps.
How did you know it was going to be bulbs and not fuse.
I’ve got the two left controls not lit up, the two on the right are fine…
That means one side is working and the other is out. Once you're at it, it's best to change both bulbs, as if one gave up, the other one may soon follow. And as for the fuses - there're normally few things on each fuse, so if you'd loose say stereo, electric mirrors.and backlight, that's telling you there's a fuse. Some items have dedicated fuses on their own, but such low amperage items like backlight will always share fuse with other devices on the car. Hope this helps.