Interestingly I live in a house with an almost identical layout, just without the extension.
Your kitchen/utility/downstairs WC is a much better use of the space than in my house though, so I may well be copying this when it comes to re-doing our layout!
I was going to say the same as many others - the photos make the house look darker than I'm sure it is. The middle dining room is listed as such on the floor plan but then the dining room table is in the extension.
I can see from your posts that you don't normally have it that way and I would agree your usual way of using the rooms makes more sense - at the moment the pictures make it look like a nothing room, whereas using it as a dining room would mean the extension room can be used as a family/play room - if you were going to move any furniture anywhere, I'd suggest this is the room the blue sofa could go in.
If I were looking to buy your house, I would be thinking that I'd want to knock through between the kitchen and the dining room to open it up and make it brighter. As a PP has said you could then close off the living room, or as I want to do when we do ours, put in glazed pocket doors to keep as much light in the living room as possible (as ours can be a little dark too)
In all honesty, I really don't think there's much "wrong" with your house OP - it's just the people that took the photos made some really bizarre furniture moving decisions. I can understand depersonalising to some extent but I'd put the pictures back up on the wall too, unless they're pictures of family members. General artwork is perfectly fine to leave up.