How about a straight run of cabinets/appliances along the long right-hand wall, with a shorter row of tall cabinets housing pantry units and fridge/freezer against the back wall of the sitting room.
Have an island to house either your hob or sink (I would choose sink personally, then have a stone top for the island and cheaper tops, e.g. wood or bamboo on the rest of the kitchen), parallell to your straight run, but closer to the back wall, connecting the three areas. I would have a big freestanding range cooker in the middle of the straight run but might you prefer an eye level built in oven? If you would, you need to house that in a tall unit.
How is your understairs space being used? Is it an option to stack your washing machine and tumble dryer in there and make a mini laundry space? Then you don't have them running when you're using the room as living space.
Put the dining table - probably an extendable one - in front of the island closer to the doors. Then set up an l-shaped seating arrangement backing onto the dining table, looking onto the short 3.7 mwall, if you want a tv, or woodburner etc there, or in a U-shape looking on to the dining area, around a nice big coffee table if you prefer setting it up for games/conversation.