my suggestions include changing the staircase to have a halfway landing never winding steps, rearrange the kitchen, pantry and laundry, lose the biw and soffitts in the guest room and disguise the ens access door within the new MPR/guest room wardrobe, side access for understairs storage is much easier to use and, by the time you load and unload the laundry into a shute it would be quicker easier and cheaper to throw the washing down the stairs and save the space for more useful purposes ..pleased to see the good sized garage...cheapest rumpus, mancave and wet weather playroom with the addition of a few lockable storage cupboards and shelves...can't see the value in the extra hot water tap and gas outlet for the alfresco..rather extend paving across the back of the house and invest in a servery window to load dirty dishes directly into the kitchen for the dw and inevitably the wind blows smoke into the house so it's better to have a moveable barbq away from the walls and...upstairs hallway narrower to allow for extra steps, rearranged ens and wiw, avoid the void and use the space for a WIL or space for a baby's cot, dressing area, and/or leave the space open and invest in a gorgeous chest of drawers for linen and use the big WIL as a study nook with a separate small lounge and rearrange the bathroom with generous storage in the vanities, bigger shower and narrow freestanding bath...without all your dimensions some of my sizes are approximate but adding furniture helps understand the spaces much better and inside of wardrobes should always be at least 60cms plus the walls an doors and it appears that the plumbing access could be in the garage instead of the kitchen?