Updating your main sitting room can be difficult. Very commonly people are defeated by the volume of objects and furniture they have accumulated previously that seems to stifle the desire for modernity and change. By choosing a classic modern style for the room you should more easily be able to travel from stuffy to sleek.
The colours I would suggest to start the theme are a neutral calm palette such as Little Greene Old paper combined with Julies Dream. Making the most of any light in the room paint the woodwork and ceiling a bright white. We are moving away from paintwork being off white as this can look sallow.
If you can ditch the curtains opt for blinds. This will immediately bring the room in to the twenty first century. The window dressing should again be light and bright but try introducing texture here with a simple fretwork patterning embossed on the fabric. You could use bamboo slats that will just hint at natural world beyond. The seating you have could be recovered and pale mushroom linen will fit in with this colour scheme. The flooring might be a lovely oak wood either new or perhaps sanded existing floorboards stained dark to add depth.
Into this subdued contemporary style I would add a shot of drama and luxury by placing a boldly woven rug. The tone here can be echoed by suitable cushions picking out the brighter hues. Equally there are opportunities for introducing more texture and shape in the lampshades and accessories you might already have.
A neutral contemporary revamp of your room need not mean buying everything new. Make the most of what you have, freshen it up and go for cool calm and collected.