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!

Where is your house? Low maintenance plants depend on the zone. I wouldn't plant in your rock skirt. Ideally you'd put your rock skirt around the house and then planting beds outside of that. The skirt keeps mud and dirt off the house and let's you spray for bugs etc. since your skirt runs right up to the driveway on that side, I think your options for plants would be some large pots or window boxes. I'd paint your foundation the same color as your grout in the brick to help it blend in.

If you are seeking a truly open feel to the floor plan you have shared, then using one material in the mail living area is the best approach to making this space feel truly open. Using a variety of materials on flooring chops up the space and decreases the visual footprint. I would suggest using wood, tile, or if you are on a tight budget laminated flooring for the living/dining/kitchen. Then use carpet in the more intimate spaces; bedrooms and possibly hallway. Save the tile for the bathrooms.