Have you thought about getting slipcovers made? If you wanted to go with a cottage look white or off white would look good with your rustic fireplace. Don't be afraid of the white, slipcovers that are made well will last a long time, and can be washed even bleached. I have had mine for probably 9 years now. Love that you can wash them. I would skirt the bottom of the slipcovers. I think it would really transform them. You could bring in some blue accents with pillows, etc. Some pictures on your wall with some ocean blues would look nice with some rustic touches like antlers, shells etc.

I agree with emily. if you want leave connections and/or a little extra room for what you don't want, but feel you may need for resale. I think the tub is a pretty important item. wet room not at all, and shower is give or take. i would prefer a big shower and a tub for soaking in, but I have always had the combo. I remember my mom built during big wet bar craze, she did not care for one. had space built, capped off connections and use as a closet. Now it is 35 years later, everyone wants to buy and tear down. Darned if you do, darned if you don't. i agree, I would also really like the separate toilet, we are not share everything people.

Have lived in places with a tiled window -- tile the sides and top as well as the ledge, so that you go right up to the caulk/frame/glass. Works to let out some steam and store shampoo too!

I agree you probably need to centre the vanity and the cabinet on the wall or they could look a bit odd! You don't say why you don't want a space between the window and the vanity - just my opinion, but I would think 300mm could be quite useful for a bin, a clothes basket or box, or a small stool for putting clothes on? The only alternative to leaving a space, is to fill it with something as the response above suggested. To avoid it interfering with the window, you could make this something lower, so it sits level with the top of the vanity. This could be built in and the wall lining put over it to create a single "shelf" level with the underside of the vanity top, or if you can find some freestanding open shelving of the correct width, which could also be cut to the correct height, you could wedge that between the wall and the vanity side when fitting the vanity. Just bear in mind also, that you'll lose some of your towel hanging space if you put something too high in the space.