Have you thought of painting the wall with the kitchen units on? I would paint that wall either the mid or dark grey from the tiles - the contrast would not be as stark as it is with the white wall.

You could also get some accessories in a bright-ish colour - maybe pink, green or yellow.

I think your instincts are good here - a light worktop would really lift the space. Maybe a lightly speckled white? Marble you will need to be careful that the vein matches in colours to those tiles or it will feel a little off. And a warmer colour on the walls (it doesn't have to be strong but it will bring the room together as one) will help. Your floor looks to have some yellow tones in it so you will need to look at greys with a yellow tone (Like FB Cornforth White) or soft greens work well with greys and white and make it feel cosier.

Definitely cost up the difference in replacing the worktops versus changing the tiles too as it may be cheaper.

In terms of lights and bar stools what look are you aiming for? Is it modern minimal and to feel sleek and streamlined or do you want something a little softer with a more natural feel or something completely different? Dependent on that it will help focus what to go for in terms of bar stools and lighting as the options are endless as I'm sure you know! From glass to rattan shades and everything in between!

Happy to help further if you need it too!

I agree with Sonia. If you don’t like them, change them to something you do. The thought might be off putting (they’re new! The mess!) but it is a reasonably small area & you won’t like them more when you’ve gone to all the trouble of choosing other decor & furniture to tie in with them.

I think the grain of the granite worktop is competing with the splashback and this may be why it feels a bit off. I would keep the worktops and change the splashback to something more subtle. It would probably be more cost effective as granite is expensive and it should be easier to match the worktops with a splashback rather than the other way round.

I’d change the splash back too. It doesn’t work with any other colours in your kitchen & is too harsh / cold grey against your cabinets, which on my screen look like a softer, warmer grey.

the backsplash is too busy - change it as per Sonia's suggestions above. the other thing that is wrong is the white walls. you have no white anywhere else in the room so it just looks like you've put on undercoat and not gotten round to painting the real colour yet. if you switched to white worktops then that would help, but i don't think you need to do that as the worktops are fine. you just need to choose a pale neutral colour for the walls that doesn't clash with the cabinets - a lighter version of the cabinets really. or paint the cabinets a paler off-white/neutral.