Switch the front window and your side entrance door, this way your door is visible from the street. Then turn the window in the pantry into a door to gain access more directly to your kitchen, a closet and maybe a bench for gathering items on the way in or out. It looks like you have to go up a small flight of stairs to get to the door, otherwise I'd say put the additional entrance on the cellar wall on the left of your plan. Depending on space you may need to slide this new mud room entrance to the left and you might have room for a longer closet along the pantry wall and a bench opposite the closet along the outside wall. You would lose the cellar but I am not sure if that is another storage area or access to a basement. Just some ideas. Really like the rest of the layout. Hope my little picture helps to explain my ideas.

Marble is a beautiful stone. You will need to have it sealed regularly (every 12-18 months and unfortunately if you're a keen cook you should be warned that it can stain and acidic things like lemon juice and vinegar need to be wiped up immediately. I say this as if you're anything like me you tend to share a lot of your cooking with your splashback. The alternative would be to look for a caesarstone type material in a marble pattern - Caesarstone and similar products don't need sealing, aren't porous and are more stain resistant. Good luck.

I would lift the frontage by choosing a complimentary stack stone colour combination (on porch frontage). Don't go contrast, but try and find some that will lighten the look. It would also create a focus to the facade which I don't think is a bad thing. You need to ensure there is a fair amount of grey tones in the stack stone (or whatever stone you are using) you choose.

Thanks so much for the recommendations guys, really appreciate it! What colour would you recommend for the splashback if we're going glass? also we might be tenant in the property, will glass be okay there? (also.... how much more expensive is thus going to be that tile? I have no idea on costing here :S) Also I think I may have oversold the messyness of my cooking haha I'm not that bad but I do worry about discolouration of grout.