The walkthrough is so much more attractive than the photos. Your picture of front-of-house makes the house look twice as big.
The sitting room is by far the worst room in the house. I would paint the wall, and again I would lay down a pretty rug. I'm personally a fan of Ikea's Persisk line as a decent but inexpensive solution to lack of color: www.ikea.com/gb/en/cat/oriental-rugs-10695/ Or you can often find proper things on eBay.
Alternately, something large and plain. Or--maybe think about replacing it altogether? It's not a huge room, looks relatively level, and would be cheap to re-floor. If you painted the walls a lovely dusky blue-grey (or even a green blue? Like www.farrow-ball.com/en-us/paint-colours/green-blue) with a nice light carpet would be a delight and would handle your couch well. Could probably get away with redoing everything for a grand or close to.
I'm afraid I agree about the furniture. It's good sturdy stuff, but it's very much not in style. So lean in to the home-y-ness with a tray, some books, etc.
Don't center the couch on the far side of the wall (as if the tv were the midpoint)--pull it away from the wall with the doors. You could put a side table between the couch and the wall, should you want to, with a nice table lamp.
You can put the second couch back in. If you're going to keep the coffee table, I'd put it with the second couch and the ottoman, with a nice throw, in front of the sofa. This subtly opens up the room. When you're taking pix of the sitting room, make sure the doors are open. Gives more spaciousness, and also they're a bit out of date in terms of style.
Reverse the family room and dining room. Agree that you should only photograph one TV.
I actually like your kitchen just fine! I'd add a few more items on the counter (e.g. fruit bowl), but it's really about angle. The original photo makes it look poky; the walk-through makes it look clean and bright.
Agree about the heater downstairs (paint it), the rug in the purple room (remove it), and the orientation of the purple bed (flip it). The purple is more clearly a lovely lilac in the walk-through.
This is only going to take you so far--the price is certainly going to be an issue. But this will help.