This is the second time I had to change a headlight on Tanya’s Opel Meriva. I learned this trick the first time:
Yup, remove the headlight cluster. Two 8mm bolts at the top, and one underneath.
Then, it’s easy to undo the clips and change the light(s).
It’s not so clear on the picture, but the arrow marked “Haut/Up” should point towards the engine to install the cover (which you have to do after putting the cluster back in). For the bottom one, up is up. For the top one, not so much.