The fading black I have seen has been on manufactured plywood type cladding. It does not look good as looks uneven and patchy. When building we changed from the cheaper cladding to solid recycled hardwood shiplap. So glad we did, as it is now greying off beautifully.

Dulux Charcoal on the timber and also paint the orange tiles under the window on the timber side. Too many orange stripes, the other two match so I'd leave them. Paint windows and trim Whisper white, paint the top gutter against the roof charcoal and the trim under in Whisper white. Also paint the door step in charcoal. Like your house, all the different textures just need to compliment each other. I'm building mid century design now, I'm using all different textures too.

Ania, can you post photos when it is finished. It will be good to see those colours combined. I also love that inspiration photo and have it saved. I don't know what particular thing makes that bathroom stand out but it is beautiful. I want those exact same colours in my bathroom but a too scared to use timber tiles as I am scared they will date so am bringing in timber via accessories such as picture frames (I think). What is the grey tile in your photo and where is it from...it is very nice.

I'd definitely pursue the skylight idea, it will make a huge difference to the feel of the room. Particularly a skylight over a bath/shower can make the room look really great and is easier to install where the height to the pitched roof is shorter. The window is very narrow, not sure as it's kind of quirky & charming, otherwise replace with another wider old-style sash window or remove all together and just use the large skylight and good downlights. 1800mm wide is lovely for a bathtub against the back wall, and will make a nice focal point as you walk through the door and change the bathroom from looking like a narrow corridor as it currently tends to. Back wiht some fresh white subway tiles which will feel lovely in your farmhouse and with that lovely traditional door and some simple traditional tap ware/showerhead. I like your built in bath reference, I know feature stand alone baths are popular, but with small children, I'd forever be mopping up awkward spaces around it. You maybe able to reuse your existing bath if it's in good nick. Then a lovely vanity with recessed mirror cabinet built into the wall for lots of storage. I wouldn't fuss too much wiht the toilet, I'd keep it as is, tucked in the corner.