It's refreshing to see nautical, navy BLUE. Everyone is saying the same thing for the most part - just introduce another color, definitely bright (yellow or orange IMO) and it will make it more current. What I really like is how your style will withstand the test of time - and with minor updates now and then it will always look fresh and "current".

Oh, okay, may need to clarify some more. If you get a new 2 seater in place of the 2 white chairs, fine, but no blue chair at all next to the 'new' 2 seater. Won't be right with a blue chair too. So what ones are you planning to recover?. If getting rid of part of it, not understanding. 2 different styles placed next to each other won't look right. I wouldn't like old blue fabrics next to new fabrics or next to 2 different styles of furniture. New 2 seater and old blue chair next to each other, not good :)

I am planning to add scatter cushions and think if I do a pair of larger ones for each end so they go over the arms to creat height at each end, and a couple of smaller ones, I want to bring some colour in too. I do like the idea of a larger side light at either end to, Switching the sofas is going to be my final fix if all else fails!!

Well, for lack of a better idea, since you find it a drafty little space. I'm assuming the draft comes in on the right? Most of the necessities in the area are located of the left side; i.e. vent, thermostat, light switch etc. What I would do I think is caulk up the drafty spots, maybe even add sized poster board wrapped in batting I covered in a gorgeous fuscia with diagonal grosgrain ribbons every which way covered with a heavy velvet to be attached to the area above & below the window. (Of course remove the drapes that are hanging in there). This for the purpose of using it as a pin-it board for notes. Attach a table height board covered in felt to carry across the full width of the little room. Leaving just enough space for a comfortable little antique desk chair. Paint the back wall a bright cobalt blue, paint the ceiling a silvery pearlescent white. Find a way to attach a clip-on task lamp. And stretch a heavy duty enough wire across the top of the opening and complete it with a heavy doubled velvet drape with a drooping valance. Place a swag with fringe & jewels on it to be closed when not in use. Voila intrigue is yours!