Do post a photo after making changes. It would be very good to see the results.

I think the old clock is a must have - heritage is important. I would start with the pendant. It is quite hard to see but what I can see doesn't seem to blend. I would keep a mirror but perhaps make it rectangular and hang it landscape, which should make that wall look wider. I would also perhaps consider getting a mirror with a wooden or antique finish so that it blends in with the clock.

Shame about the clock. It's the only piece that doesn't look modern or match the rest. I agree with the others that the pendant has to go and replaced with three medium-sized metal ones. A nice silver frame rectangular mirror will look nice just to break up the all-dark look of the room and also match the three pendants.

I'd remove the mirror as I think is making the walls too cluttered and unless its a very decorative mirror, it just clutters but doesn't add any interest to a room.

How about just swap the art work over with the mirror (& try the mirror landscape above the side table) can you change the color of the pendant (spray your favorite color to make it pop)

I like Wilma's idea and also Kelinnz's - thereby putting the clock where the mirror is and the mirror where the artwork is. I think two large objects are vying for attention which is the problem. Room looks great though I can see a wonderful Christmas day going on there.

Turn the mirror sideways and put over the sideboard and then the outside garden will be reflected. Put the art work where the mirror is now. I ave certainly seen masses of rooms that look much worse than this one. Good luck with whatever you decide.

White chairs!! They will lighten the room immediately.

Perhaps try swapping the clock with the side cabinet (centering the cabinet with the dining table) and placing the clock in the centre of the wall between the breakfast bar and the door. You could also try a centrepiece that in some way replicates the hanging light. This may make the room appear a bit more balanced.

Everyone has some valid points and so I would also recommend moving the clock to the kitchen wall and place the wall unit under the mirror. Centre with the table with the additions of some artwork each side if the clock with wooden frames to match the clock. Find a low piece of glass or pottery or a runner to tie in the grey shades. I presume u have a grey lounge suite. Change the lighting as to what was suggested by People Space ARchitects.