It is a tough layout to work with - this might sound unusual & I'm not sure whether it would work 100%, but if you create a 'freestanding wall' with your bookshelf (or perhaps get a new one in white), with a low entertainment unit next to it, then shift the lounge against the long wall, you could possibly create a room rather than a space that probably feels like a corridor. Here's a very quick scribble to show you what I mean

In your climate fly-screened, cross ventilation is crucial and louvred windows are a great way to achieve this. Your kitchen windows are spot on, and an additional fixed, glazed window behind the cooktop will not contribute anything as you already have planty of light. For your butler's pantry I would ensure that you increase the size of the louvred window as much as possible to ensure good cross-ventilation with the southern cool side of the house, which will also make it a nicer space to be in. Best of luck, Dr Retro of Dr Retro House Calls

Thanks for supplying ceiling height info, something for you to consider with your renovations, legal ceiling height in habitable rooms is 2.4, hence my question. Do you have actual ceiling height of the "sitting room" Habitable Room and Legal Ceiling Heights According to the "Building Code of Australia" a Habitable Room is: "A room used for normal domestic activities and Includes a bedroom, living room, lounge room, music room, television room, kitchen, dining room, sewing room, study, playroom, family room, home theatre, and sunroom; but, Excludes a bathroom, laundry, water closet, pantry, walk-in wardrobe, corridor, hallway, lobby, photographic darkroom, clothes drying room, and other spaces of a specialised nature occupied neither frequently nor for extended periods." Building Code Ceiling Heights A room or space within a building must have sufficient height suitable for the intended function of that room or space. According to BCA Vol 2 part 3.8.2, for the requirement to be satisfied, the ceiling height must not be less than: in a habitable room excluding a kitchen - 2.4 m and in a kitchen, laundry or the like - 2.1m and in a corridor or passageway or the like - 2.1m and in a bathroom, shower room, laundry, sanitary compartment, pantry, storeroom, garage, car parking area etc - 2.1m and in an attic, room with a sloping ceiling or projection below ceiling line or non-habitable room or similar - a height that does not unduly interfere with the proper functioning of the room or space. More than 50% of the ceiling space should be on average a minimum height. in a stairway - 2.0m measured vertically above the nosing line. Otherwise, the room would be deemed to be a "utility room". Technically the height is measured from the finished floor covering to the underside of ceiling or lowest protrusion of the ceiling. If you are trying to determine whether you can build in an area - ensure you take into consideration what you are going to put on the floor. If there is any doubt about a ceiling height - you should speak to your local council: Do you have a Photo of the current front door

my suggestion for the master suite depends on location of the windows but removing the biw and changing the location of the master bedroom entry door would allow enough space for an ens and wiw with 4.2m of full height storage plus space for a tall chest of drawers and plenty of standing/dressing area and the ens would allow for double vanity and 1200 x 900 shower depending on the exact width and location of the big window but i've included an alternative with a small desk/dressing table/chest of drawers in the bedroom if the big window is too wide or can't be changed BUT always depends on accurate dimensions and your measurements of the other bedrooms and family bathroom are inconsistent so could you please confirm the size of all the rooms, including the entry, hall, wardrobe and pantry..and what is the height of the downstairs ceiling as there may be a small amount of storage space that could be located above the stairs (behind the present location of the fridge??)