My initial thought is it May make the room fell narrower doing the short wall opp door. Might be ok if not to great a colour contrast. And if it is beautiful that might be the way to go. -other views?

after tiling to the ceiling in my high ceiling old bathroom i've decided that "next time" i would prefer to keep the tiles in line with the top of the architraves around doors and windows...tiles are there for a long time and so many tiles make me feel like i'm in a public bathroom and although i love the look of the new bathroom i miss the opportunity for some colour and/or texture with paint or wallpaper that can be changed so much more easily, cheaply and more often that extra high tiled walls

I really like that floor. I hope you are able to keep it once the complexities of waterproofing are revealed. Really large tiles would not be era appropriate. And they were moving away from subway tiles by then. Perhaps 20-25cm square in running bond for that decade? Colour will be easier to pick when the green is gone. I think bright whites could be useful accents but were not really available back then, except whitewash. So depends on how true to the age you want to be or if you’d prefer to have your own blend of the best of two eras.

How big are the floor tiles? It may look unbalanced with a more delicate tile in the floor and the 600x300 on the wall. Are you able to continue the flooring tile up at least one wall for cohesiveness.