@BoxRoomRefurb my daughter is in our box room and the window wall is actually smaller than yours. Ours is 195cm across the window, so we have just shoehorned a single bed under the window and it touches both walls. Our only radiator is also along this bit of wall, so she’s right up against it in bed.
As we walk in, our door is on the same wall as yours but on the right side of the wall, not the left. We walk in and behind the door on the left is a double wardrobe with sliding doors. If we do a 90 degree left turn from walking through the door, the mirrored wardrobe doors face us and because it is wider than deep, it gives a small amount of floor space between the front of the wardrobe and the door. My daughter has some pictures on this bit of spare wall.
If we walk through the door again and face the window, on the right side, in the gap between the door and the bed is a small desk. We got it from B&M’s at Christmas and it’s very compact but with a shelf underneath so it provides extra storage. My daughter can sit at this and is really comfortable.
My daughter has a tv on the wall at the foot of her bed and underneath, had a narrow shelf. It is actually a white ikea picture rail, but my daughter puts art and other bottles and deodorant on it.
There isn’t a lot of floor space, but surprising it isn’t cramped and feels really cosy. She has everything she needs with a bed, desk and double wardrobe. To make the storage work even better, we bought a small set of drawers and put them in the bottom of half the wardrobe. She uses this for underwear, pjs etc.
We were very restricted in buying a bed as only a divan would fit, however, with that extra bit of space, I’d try and get an ottoman bed in as it will provide storage underneath and is easy to access. Our window wall is so small that we had to buy a headboard and fix it to the wall above the bed, as there wasn’t room to attach it to the back of the bed.
I hope that helps a bit.