If you have bare walls, then choose colours that won't clash and would tie in wiht the room. Then pick out colours you actually like and pick a favourite. Most everything will go with Grey but contrast is usually more visually pleasing.

Stacked splashbacks always look wonderful!

Hi Davina, either way would look good, so don't stress about it too much. This is a similar set up to our kitchen and I went with A & B both tiled and haven't regretted it. It looks generous and is more practical. Tiles are best around food prep areas as they are easier to clean than a painted wall ... you think that the splash back is what gets the most dirty but the walls around it get their share of splashes as well. In terms of suggestions for tiles - we went with a white textured subway - boring I know, but classic. Using a darker grey grout to match your bench would look good. All the best with your renovation!

What an amazing transformation! I LOVE those cabinets!