I like Option 2 honestly. Obviously you are finding it hard to visalize what the space will look like but honestly that is a huge space so I would recommend putting in the utility considering what you gain from it. You gain a space where you can block out the sound of the washing machine- who wants that sound when your eating dinner? Also washing is unsightly- do you wants piles of clothes in your nice brand spanking new kitchen? In terms of the corridor you are going to have lots of light coming through from the new extension. When you enter the front door and can see straight through to the garden spaces feel much bigger than they actually are anyway. Also who says it has to be boring. Have some fun wallpaper or colourful art hanging. Also if you want to make something more spacious use sliding doors for utility and wc. Less items infringing on corridor space. And lastly, the reception is purely personal preference based upon how your family function. Personally I prefer two rooms. Allows for more space to get away from the open plan area. Mini adults room and a kids room/study. Hope this helps

One of the plans above relies on removing the kitchen access to the utility so the solution is to make a wc in your laundry room. You could make your kitchen bigger by putting the toilet under the stairs and having a laundry cupboard. If the kitchen was a little larger there would be room to put a table on the end of the island. This could be extendable and could spread into the tv area for high days and holidays.

@Jon Burchfield thanks, that looks really nice! Slight issue is that we have a pitched roof on the new side infilled area. Unfortunately planning constraints mean that the height at the wall will be 2.6m falling to just 2m. I know the velux windows are recessed into the roof but if we have tall units on that side it might block out the light, how high are the units? Having a 450mm unit in that corner would be practical but I think it would look a little odd if we had 600mm units next to it. Perhaps 450mm either end with 3 600mm in the middle would look ok? @Mark Bassage @kwg kwg Thanks. Take on board the hob suggestion from everyone. Seems sensible to have it on the other side. The oven/microwave is a tricky one, if we go with the peninsula design unless we have them under the counter then the only space would be just on the left as you enter. That's practical, but we're slightly concerned this ruins the nice open feel you would get to the left as you enter. @i-architect that is something i'd considered, first impression from the company is that it would be possible but i'm not sure why. I'll check with the builders. It would make access to the under stair cupboard a little trickier but might be more practical to make the most of the kitchen space

Thanks for the replies. There is only 3 of us but we do use the dining table every day. Our current one won’t fit, so intend to buy an extending one when we move in. I did think about the under stairs cupboard, but it slopes and we need to keep school bags etc somewhere tidy! I was hoping to put the dining table in the breakfast area, the owners now have a round one in there along with a side board, so hopefully should fit. Thanks Jonathan, never thought of putting it that way! Will look into this