I don't feel you need anything. It is excellent as is. The series of etchings on the wall draws the eye and gives depth. When you have dinner parties, I am sure you must lay it beautifully.

Difficult to comment when we can't see an image which is needed really when you're talking about mixing styles. It can/can't work depending on the situation and products involved. How about recovering your existing chairs?

You could no doubt pay a carpenter to make this for you for a couple of hundred pound plus materials. Oil it yourself to save more cost, plus it's easy to do.

Hello, this is a classic example of a 'side return extension' where you square off the building to the width of the full house. If you filter using this phrase you will see examples. You have choices here. You could put the dining room and kitchen together, and wall off the lounge to make it a separate room. If you want to extend the depth and go into the garden also fine but you are left with having to walk through the dining room to get to the kitchen. I would definitely extend the dining room into the kitchen. You will find that you will spend most of your time in this space. Do you intend to move out or live in whilst the work is ongoing?