A few simple suggestions.
1. Lose the vestibule It is too small to be of any use, we have a larger one currently and still stand in the hall whilst people walk through. I have done away with it in the new place. Without the vestibule you will have a much larger and more pleasant area in front of the stairs.
2. Could you put the washing machine in the hot press? Depends on if you like to hang washing outside, but if you use a dryer, then keeping all the washing upstairs is a lot easier.
3. I would always rather have fitted wardrobes in bedrooms if possible.
4. What was the architect thinking with the chimney up the middle of the wall in the bedroom. Does the lounge really need such a big fireplace taking up a lot of room. If it does I would try to route the flue out the wall, not up the way. Decide what fire you want before you start, it has been a nightmare trying to get fires to fit with all the flue requirements.
5. As mentioned try to get larger walk in showers without doors.
6. Move the door into the kitchen/dining room behind the stairs. Walking in facing the island so close to the door will feel quite unpleasant and will be bad for circulation. It's better to enter the middle of the room with the option of going right or left. The dining area will also probably be the quietest least used area so better to walk into. You could then have a straight stair and wider hall.
7. Turn around the WC and enter from the hall. You can then lose the rear hall and incorporate it into the utility room.
8. There are currently no cupboards downstairs, there will be space if you lose the rear hall and rearrange that area.
9. Put cistern and pipework under the eaves in the upstairs shower room.
10. How low exactly do the walls go in the bedrooms? If that roof slopes at 45 degrees in the master bedroom then you will end up at floor level at the end of the room. You might have to cut a metre off the room. I would not really want to end up much lower than 1.2/1,3m at the side wall. That room might be much smaller than it looks. Even the other bedrooms may have an issue.