I can't see the whole room....the comfy chair looks so far from the couch and not fond of the TV in the corner. In the third picture, I see a table or something in the corner by the TV...what is that? Without seeing your whole room, could the TV be put flat on the wall on the other side of the fireplace and the chair nearer the couch, slanted enough to see the TV? I would take all things off the mantle and hearth and depending...try the mirror vertical instead of horizontal. Then on the left side of the fireplace, an accent chair (for conversation not TV watching) with a floor lamp and some sort of pretty art to go with your color scheme.

Hi there. Thanks ever so much for your advice. That's really helpful. Here are some more pics which I hope put things in more context. Sorry but taken at light so no natural light! The cat wasn't for moving....

Since you're working on this room, here's an article about curtains that may be helpful. They should either just touch the floor or be less than an inch above.

https://stylebyemilyhenderson.com/blog/hanging-curtains-all-wrong

I agree with graywings123 in regard to moving the sofa in front of the windows and putting the t.v. where the sofa is now. Consider a bit longer console for the t.v. to take up some wall space. Furniture glides make it easy to move the furniture around.

The fireplace mantle/hearth is an odd size. It seems awfully small and it looks hard to decorate.