I you are changing from stacker to bi fold doors you should ensure that there is a single door included within one of the bi folds, preferably next to the kitchen. I wonder why you are deciding between white or black windows and doors for this room when you already have white elsewhere. What colour are the internal and external walls.

Not quite sure what colour your windows are but check this group

I'm of a similar thought -- the new addition in black looks smart , and suits the style . I'd be tempted to do the fixed window in the first pic ( the dining area ) in black too , preferably by replacing the existing window , but possibly by painting as a budget measure -- it doesn't look right to me , either from the outside or inside , whereas the smaller windows in the lounge etc looks fine in white -- almost what is expected . I'd stick with white for the gutters and eves too -- the dark roof and dark brown bricks would look too bulky with black or charcoal or brown or any dark colour IMO -- it needs that light coloured break !

Absolutely, would look stunning. Just adding the black on the doors would be just beautiful