I light grey/off white would look fab. It would lift it and help bounce the light around. Perhaps a large mirror would help too. It would also ties in the dining chairs more and compliment the work surfaces. Good luck

So you get sun for a good part of the day which means the room is quite bright. The black sofas are light sapping, so if you are keeping them you need the throws and cushions to help brighten them up. I rather like your dark wood furniture and they will be improved with plants to give a bit of a colonial or tropical vibe. You could wallpaper one wall in something a bit tropical to add lovely greens. Some are quite colourful so you can pick colours out for your accessories. In which case a nice soft white on the rest of the walls would look great. The wall behind the tv and table looks like a good wall to wallpaper. You can’t deny it gives you plenty of colour!

Hi, I can now see the bigger picture here. This problem is very similar to one I looked at the other day on Houzz. I general I would always recommend using the dining space as circulation rather than the kitchen or sitting area. I suggest that you just look at the L shaped room and ignore where the doors and windows have been placed initially. You have an understandable requirement for 3 primary spaces. Kitchen, Dining and Sitting area. I would suggest that you have a U shaped kitchen in the niche space to the left hand side of the double doors as you enter from the hallway. Have a window to the garden from the kitchen not a double doors. To the right you have copious space for dining and then the whole of the new extension can become the generous sitting area you desire. I would suggest a door to the side elevation and picture windows looking into the garden. The addition of a peninsular or island unit as a breakfast bar is optional. Please make a donation to shelter https://www.shelter.org.uk/ for this advice

I know grey is the in colour but don't you think that it makes the room look cold? i prefer the other picture as it looks light and airy