after watching my daughter and her husband agonize over the way their expensive timber floor has not held up well after 3 years, I would recommend tiles/wood look tiles with under heating. Their beautiful warm expensive floor looks like it always needs a clean and polish, not from neglect, they have cared for it well. One of the boards now has a slight and painful moan when it's stepped on :-( I grew up in a completely wood floor home and although it looked wonderful, my Mother hated it. ....and the mats ! Wood is a lot harder to maintain than tiles ,(no matter what the die hards say) the modern wood finishes are much better than they used to be.... But a piece of wood is rather arty no matter what it's used for and it does demand to be loved and cared for.....and if something goes wrong it's a lot more expensive to fix than sand and cement. Ultimately you have to be happy. BTW underheating tiles is warmer than timber :-)

I wouldn't do skirtings . I'd do the floor tile for '1 tile' up the wall ( assume they are 200 x 200 or 300 x 300 -- cut them if 400 or 600 ) . Personally , I'd probably even do the 'silver' tiled areas in that 1 height darker tile too , as it would make the whole room look more 'level' , but thats up to you and your tiler .

Used beveled subway tiles for whole bathroom without thinking about internal corners so the corner looked terrible then the silicon went on and it still looks terrible I guess apart from an aluminium strip or a marker to go across the silicon there aren’t many options

Eh ? You want white or off-white or similar ? Your kitchen is white and off-white , with quite a light wood . And a nice red toaster . I have noticed the toaster , and commented on it . You have purchased the toaster . Other people will notice the toaster , and comment on it . Because it is the only mildly interesting thing in the kitchen . Dark grey doesn't sound interesting , but charcoal does , so I am hoping it is closer to charcoal than dark grey . Am I overly optimistic ? Can you swap the dark grey for black gloss , because I suspect black gloss subways would look quite good there , and tie in the oven and cooktop too . Now what would happen if you were stuck with the grey or charcoal , and went out and bought a dozen crisp white subways , and a dozen Red subways . Get your 30 or so charcoal subways , and lay them out in a rectangle on the floor . Take 6 out in a reasonably random way , and put white ones there . Then take out another 6 , and put red ones there . Depending on the grey/charcoal , it may look crap , or it may look okay . If it looks okay , put the dozen grey ones on the top , take a few more away , add more red and white . Overdone ? Underdone ? Have a play . Don't like it ? Get all the grey ones , and 'stand them up' ( lay them vertically ) . Lay a line of red ones horizontally across the top , another line of white ones horizontally across middle . Swap them . Don't like any of them ? Get some brownish Tavertine Tiles , or an Orange ( or red or yellow or citrus green or your favourite colour ) glass splashback . Experiment . Put the on the bench and imagine . Thats what I'd do anyway . But I wouldn't do only dark grey , and I probably wouldn't do charcoal on its own , but I'd see first .