I have a double right now (one large, one small) and I use the small one to drip dry anything that doesn't go in the dishwasher. It's convenient, but even so I'm planning to switch to a single large sink in the future. I haven't found any double sinks that I really like, but I will admit I haven't seen a great solution to drip drying pots and pans. I really do use that second sink a lot (even if I towel dry my pots, which I don't usually bother to do, I still have to have a place to put them until I've finished the dishes). Most dishracks I've seen are intended for plates and utensils, which I just put in the dishwasher. If I can find a good dishrack for pots and pans, then I will be very happy with a large single basin sink I think.

Our island is 900 depth, 2400 wide, with a sink in the middle (opposite the cooktop), which works well for us. Plenty of prep area either side of the sink (mind you, it's a single undermount sink, about 500mm wide, with no drainboard). If we were going to use the island for actual meals, ours is only deep enough for a person either side of the sink. So, if you're thinking of having the island as a dining area, go to the 1200 depth. Just walk around it to clean it. On the other hand, if the island is going to be for prep, and a place for guests to prop up a glass of wine and chat while you're getting dinner, 900 is fine. Our dishwasher is to the immediate left of the sink, and we have pull out waste bins underneath the sink. We have 1200 mm space from island to the wall side and the range top, and about the same to the other ends. Our fridge, which isn't huge, is in a 900 mm+ cavity which would be big enough for a deeper fridge. It's in relatively the same place your fridge is, and works fine there. Hinges are on the non-kitchen side of the door, so it opens into the kitchen. Cabinets beside it are a bit more in depth, so fridge and cabinets line up nicely. 850 for your fridge seems reasonable to me. I wouldn't put that study where you have it: I think you'll need all of that butler's pantry for butlering type storage. My 5 cents worth based on new house, new experience, absolutely no kids in the equation!

My 1 1/2 square sinks are 40 x 340 x 20 & 40 x 250 x 20 , big sink for big things and the smaller for smaller washes and vegies, water can be deeper than the bigger sink this helps save water

we are renovating an existing laundry so not worth the plumbing for the sinks at seperate ends. its not a huge laundry - room for a sink, washer and dryer on the ground, then dirty washing. we will have overhead cabinets for detergent etc. i just thought the double sink might be handy for when one sink is in use for soaking you can use the other sink to wash your hands :)