There is insufficient under floor space for a deck to be done well. Timber really needs room to breath otherwise you face the possibility of cupping (when the boards bow upwards on the edges). If you want to deck (and it would look OK) you may have to remove the concrete and lower the floor area (ideally above 300mm) - The porch area could then be extended. Your other option is a timber look tile (yes they do exist) or just tile the floor)

all heaters and stoves should have very specific installation instructions including distance above the stove to any mantlepiece and i suggest you start with advice from local suppliers and then confirm with specific written instructions from each manufacturer that you can usually find on line...There are a number of heaters that have wood fires that are designed to be inbuilt in a purpose made wooden frame so hopefully this can be done inside your opening

Get quotes on timber and tile. Tiles can be cheap but the laying is quite expensive. You may be surprised at the cost difference.... it could be quite close so don't discount it all just yet. If you have resale concerns then avoid laminates as they're seen as a cheap choice. For me I'd grit my teeth and pay for a solid timber floor everyday unless in wet areas where I'd use a classic and timeless tile.

It's a shame that the door slides towards the shower because the first thing you see is the toilet. Could there be any other place for it? I love your inspiration photo but the two examples you have shown are not as inspiring. I would try a few more options before you set your layout in stone. I like the idea of the white vanity with the wooden top and try to find the black and white basin. Our best eye level storage is a recessed cabinet with a decorative mirror beside it. I can't understand this obsession with storing all the things you want to use behind the mirror you also want to use. Love that idea of tiling the kick-board to match the floor. I have also put mirror on the kick-board for the same effect. Wall hung cabinets definitely give the appearance of more space but do you out of some storage. I dislike the idea of a wall of glass at the shower unless you are a fastidious house wife because after a few years of being subjected to soap scum they can become cloudy and that can be permanent as I recently discovered in a rental property. In a tiny room the area can look larger if your tiles are laid on the diagonal. If you are forced to keep the same layout would you consider a piece of furniture for the vanity? Good luck. Remember the planning is half the fun.