We've had the 6 seater Seno in walnut for 3+ years now and it's prob my favorite piece of furniture. Even with 2 kids it has minimal wear and tear. Assembly was easy too! We went with white chairs with natural oak legs like this https://www.allmodern.com/furniture/pdp/avers-dining-chair-a000830483.html?piid=437144378%2C437144360 I can't speak for the extendable model, but quality really is great. More on reddit.com

I'm in the US so my search won't be very helpful, but I had a ton of similar options come up using Google Reverse Image search. Give that a try if you haven't already! Edit: To be fair, most of them weren't adjustable, but there were a few that were. More on reddit.com

I definitely feel like you need to have end tables the issue with a coffee table is that most people put it so far away from the furniture that you have to really lean forward to get a drink or something and that's not always the most comfortable thing to do. I feel like there's too much of a gap between the sofa and chair at the one end that sort of space I would love to see a really good size round table to add some depth to the room because the chairs are very square and the sofa also has a boxy look as well. I'm also not fond of the shape of the coffee table to be used with your style of furniture I would much rather see a rectangular table because of how boxy and square the sofa and chairs are because the ends of the coffee table are in front of the chairs I just think a rectangular table would blend in better and having two good size round end tables will add some depth. More on reddit.com

I like the round one better, but I would consider a wooden one or one that can pull in some accent color around the room. More on reddit.com