You would have to ensure that there's suitable insulation in the Nib and western walls in the extension the cavity brick in the original part of the building should be OK remember vergola its an opening pergola you would be advised to get a quote but this would certainly work and look better it doesn't have to cover the whole deck

It will look fine but I’m not sure how it will feel when you sit on the chairs with the front legs on and the back legs off. But unless you order a custom rug I think that 240cm is the biggest you’ll find in retail.

For the last 10 years we had a square 8 seater dining table within a square ‘room’ in an open plan space, it should have worked perfectly but it never really did. If you have an odd number of guests or 6 it looks weird with empty spaces. Finding a square rug was tricky and expensive and by adding a buffet at one end of the room it was no longer square. A round table is tricky if you want a rug under it - a round rug needs to be huge to accomodate chairs being pulled out and square or rectangle rugs underneath it also look strange. As part of a recent Reno we went back to a rectangle shape and it works much better. We often use it for dinners of 6- 2 on each side and 1 at each end. 4 is also easy. If we have 8 we do 3 on each side & 1 either end. You can also do bench seats and squeeze even more in then push benches under the table for more space the rest of the time. Hope this helps.

Thanks Dreamer. Hubby has a real hatred of bar-height eating. He was emphatic that we would not have stools to eat at the island. It had to be regular seating at table height. We will have a small table in the square space but the space there is quite restricted. It will be just for the two of us. I agree with you about the drawbacks of banquette/bench seating, but as it will generally only be for occasions when our daughter and her family join us for a meal or those rare occasions when we have guests staying over, I think I could live with it. I guess it depends on the size and configuration. It might be able to be set up so that two people sit on the bench and get in from either end, then two sit on the other side and two at the ends, as you have drawn it. It's just a question of how much width is needed, because I don't think 3m is really enough for a regular table and chair arrangement? I'm quite content, though, for the seats on the left and at the ends to be moved there from elsewhere for the meal and then put back afterward. Only the seating on the right needs to be permanent.