my suggestions (subject to accurate dimensions) include the new ensuite with extra wide mirror doored wall cabinets) a dressing area in the hallways adding a biw to the small bedroom and updating the family bathroom would allow for more generous shower and vanity and a handbasin in the toilet (and the small rectangles in the dressing area represent chests of drawers)

siriuskey, Yes, the courtyard is open to the sky (no roof over it), I assume this is what you mean by double story. Ref. below photos, I would love to get this look, especially the first and last photo, where you can see family living space from the first floor. I can't achieve this in my plan as it eats a lot of floor space upstairs. The referred plan (photos) has a very big void combining staircase, hallway and dining area. I know it is not easy with cooling and heating when you have such a big void. So, I explored a few ideas (with my limited knowledge on this topic) before achieving the current floorplan. I have also thought about, in my current plan, extending the void on the staircase to the dining area (it is more like L shape) but i wasn't sure if that makes any difference. keen to hear your thoughts.

Hi Badobbs Structafloor will only span 600mm unsupported in the 22mm and 450mm in the 19mm version so no, it alone won't fix your issue. A simple fix would be to pull up the floor in the affected area and then 'pack' it up to level, THEN lay some structaflor over the new supported sub floor. This is done by getting a laser level and marking out the low points in the joists then making up packers to suit, or installing a packer and planing it down to suit. It depends on the level of dipping. It will be your cheapest option and definitely a job for your carpenter (unless you're handy). Regarding disturbing the floorboards that is nonsense. If there are other issues such as other sagging floorboards then you can address them at the same time, or fix them down properly with screws. I suspect that the real issue is that the wall removal did not take into account that the floor joists are usually fixed to it and they are now unsupported. If you get under there and find issues with your joists/bearers then it is not a big deal to install a couple of stumps/connect bearers to support them whilst it is open. We do it all the time. Either way laying a new floor over a subfloor without addressing it would be a waste of money and will degrade your new floor. Cheers

I agree that it can be upsetting at this stage but your timber will all darken naturally and the difference will become less obvious over time and once you have furniture and rugs in place it's likely to be one of those issues that only you and no one else will notice. And I defy anyone to not have something like this in their house which has been newly built/renovated. I know this isn't terribly helpful but I don't think ripping anything up to start again or going to great lengths to seek recompense from supplier/installer is going to help your blood pressure either (by all means raise concerns with them and ask for suggestions from them).