I don't believe there will be much difference in price between a glass splash back and stone. I believe the white metro tiles and grey grout (repeating the grout to the floor tiles) will work very well, and my preference would be a matt finish. Kitchen accessories and the oak shelf will avoid it looking too bland. Alternatively, you could opt to make a bold statement by using some of the wacky tile designs that are out there, but then I would suggest considering using a white shelf opposed to oak so the tiles take centre stage.

Sorry, didn't realise you wanted to pain the units, thought you wanted to paint the walls. You'll need to get a colour that goes with the floor tiles, which I think are grey. Matching two greys together isn't easy. It's only really made possible by either taking a floor tile to the shop and picking out colour cards that you think will go with it, or just collecting the cards and taking them home. The rug on the floor won't be helping in the kitchen as it sucks the light. The dining area is lovely, albeit for me, there's just too many things in there. For instance, the objects on the table, two urns, a candelabra, two further candles and a votive glass? One object only is enough, the urn or the candelabra. Why also the need for a bench behind the table? It's nice to have things placed just so, but too many make a room look crowded. Your eye should be drawn to an object or two. I think a little de-clutter at both ends would help open up both rooms. Placing too many objects around and not keeping surfaces clear also sucks light from a room. Try clearing the kitchen out so that you get a proper sense of the space and then it may be easier to decide upon a colour. The worktop can't really be seen, but you need to take the colour of that in to the decision making also. . I'd also remove the blind as that doesn't help with light. I notice that you only have 3 spotlights in the kitchen. If that's not enough and it's still dark in the day when you've removed some of the stuff on the walls, then you could consider extra lighting with daylight bulbs. We have those as we're north facing and live in an old cottage with low ceilings.

I think the worktop is down to personal choice, I think maybe i'd go for the white if it were me. I don't like the tiles with either of the worktops though. I'd go for an up stand and / or different tiles. How about a frosted / matt / brushed glass splash back to match the same colour as the worktop. I recently ordered one from Splashbacksuk had it finished in the same f&b as the walls, looks great.

Oval dining tables are able to seat everyone comfortably and a good choice. Not so easy to come by however! Maybe a glass top table would add a bit of sparkle/bounce light around the area? If you have kids an oval or round extending to oval best. My dining table is oval with extra leaf added to round top and I keep it as extended. Might be easier to find round to oval than just looking for fixed oval top? Choose a sofa with neutral but washable loose covers (ie machine wash) and add colourful cushions to make a statement. As your wood in new kitchen is dark and warm tones, follow the warm tones with dining table/chair/sofa legs in dark wood.