Start by making a list of what you would like the room to include: size, windows, flooring etc. Then find a trusted architect to do the plans.

I would suggest you take out the cabinet that is to the right of the stove and use it elsewhere in the house -- perhaps in the bathroom or dining room with a hutch above it. Then, I would suggest you have someone install a lazy susan cabinet in the corner between the sink counter and the stove, meaning you would move the stove down a bit and have a small cabinet/counter top to the right of the stove. I would suggest you have the cabinets refinished in white and then paint the walls a pastel you like. If you would prefer white walls, then add white-painted crown molding and paint the ceiling a light neutral blue, such as Sherwin Williams Niagara Falls Blue. Then, I would suggest you choose a favorite accent color and use this sparingly in accessories like towels, pot holders, small vases or floral arrangements, and a valence above the triple windows. For a genuine 1940s look, you might have white ceramic square tiles with a rectangular red border installed as a back splash behind and above the stove. If you are replacing counter tops, I would suggest a light color such as white with a beige or light grey vein or striation for some sort of pattern. You might be able to find the same color and design in floor tile OR opt for a wood floor as another poster suggested.

I quite like the colour scheme, it's looking good!

I would consider a small retaining wall perhaps 2-3 planks high this will provide support to the bank but also allow the pathway to remain clear and formal. The ferns seem to be doing well but could do with a tidy up. I would also prune the tree so it allows a bit more light into the section to help prevent dampness, you also want to take it away from the house, without destroying it's natural shape. As ferns seem to naturally want to grow there, you could continue that theme. Perhaps some other shade / cooler temperature type plants with some flowers could be a good addition. I am not sure which plants can tolerate the cold Dunedin winters, so you best contact is your local garden centre. You want plants that are lush all year round. Also have a look at other plants growing in the neighbourhood as that will give you a good idea of what does and doesn't do well in your climate. Good Luck.