Timber with timber can work brilliantly, and it's in keeping with the mid century style you want for your home. This room (below) is a little similar to yours, albeit with less of a pitch to the roof - the large feature lighting helps to break up the expanse of timber on the ceiling. You have a lovely open plan area, so I'd be inclined to use rugs to create zones and a cosy feel. Rugs reduce the impact of a large expanse of flooring material. They have the benefit that you can swap things around to change the look and layout at little cost. I think one trick may be to define your "walls" carefully, and paint these before you go with a new floor. This should give you a sense of whether the timber is overwhelming, and how to balance it. E.g. You might decide it works best to paint the kitchen cupboards to white, to give you a more seamless look and work with your new counter tops. If you want to experiment with the "paint ceiling" approach - gulp, it's a big one!! - then maybe that small section above the kitchen bench, at a different angle to the rest of the roof, could be the spot. It seems to have the same horizontal line as the wall, so even if you don't like the painted look for the whole, you might be able to get away with blending this into the walls. Best of luck!

Love the inspiration pic. What makes it work is the contrast (between horizontal and vertical features) and the balance (between sizes of the different elements). I'd strongly suggesting sketching up your wall, either by hand or electronically and play around with the dimensions of the timber feature to ensure you achieve a good balance between your windows, the timber feature and the matrix board.

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'm guessing that a problem could be that the boards will shrink and create drafty gaps so i think my old builder dad would have laid the boards upside down, without nails to settle to the temperature and moisture in the room while he did other jobs for a week or two and then turned over the boards and, using a solid timber length to push the boards tight as possible before nailing and he would have probably appreciated the idea of adding some under floor insulation as well