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.

Not keen on tiles ... prefer a smooth surface with no grout lines to try and keep clean

Your layout for you kitchen looks really good and would fit well with the mixture of black and white cabinetry. With the lament bench top, we would suggest melamine (entry level cabinetry) or acrylic bench top, which can come in high gloss feature or matt. The matt surface would go lovely with your choice of bench top, and acrylic is also a affordable cabinetry material. Below are some examples of how Reno4u has incorporated both black and white cabinetry together, without making it to dominantly dark. We feel as if these examples would be perfect for your layout, and depending on if you want more black cabinetry or white you can go either way. This design above is an example with more black than white, can be made matt or gloss with different handles/splash back and wallpaper. With a u shaped kitchen similar to yours, however from the pictures you provided your style may include different design below the island bench. Another kitchen designed by us which shows more white than black, with a bar built in which may suit your design better. We hope this helps you, please feel free to call us on 03 423 9067 and we can provide a free quote for materials and kitchen design, and help you finalise your design further. :)

A lovely rug on the floor would be nice. You seem to have some space, yet your table is pushed against the wall. You could consider a bigger table for centre of the room or making it into an office / desk / book shelf / comfy chair. You have lovely sun coming in. Even a bean bag and a small coffee table could make a difference. A medium sized plant would also look great. Set a budget and stick to it, re-purpose things if you can and / or buy second hand so you don't break the bank. I love the little air vent on the floor it looks like a little mouse house. Maybe you can get some removable stickers and make an art piece or at least a little mouse running to the hole.