That is a good point. I have thought of staggering the line at the back. Unfortunately that would not work with our garden as we have limited space at the back and the extension would shade a large area. The current living room is small and I am concerned we are creating a long narrow room. We have got used to the cosy space but when the family return home it is too small. The living room at the front will be more a snug/office space when we are finished. I am attaching some photos of the current room/conservatory.

Good shout - BUT if I was going to spend any money on that complete waste of space I would brick-up some of the windows, put some sort of hipped-roof on it, insulate it, and turn it into an actual usable space. It will now stay as it is for the foreseeable future and the doors will remain permanently shut with it not being used again for 7 months (April/May'ish) time for a couple of days before its gets too hot. This is the single thing I hate most about our house, it's frustrating as it's such a dead space. I even hate it more than the bidet in one of the bathrooms which wastes space and is pointless (apart from my 4 year old using it once to wash her hands as she thought that it was a childs sink)

Here's a pic from last week inside (mid renovation!) I don't have one of it open. It doesn't open flat, 90 degrees, that was a compromise. Our plan is to have a table or shelf outside under the window so we can serve food out of it in the summer. I just got it from a local guy in bucks, IMI Installations, he has replaced all my windows in the past year, and made various suggestions for this window based on what I wanted to achieve.

Go for the cheapest option, it's only a door and a window. As you are planning to have alot done at the same time, spend your money wisely. You will already be adding value to your home by adding another room and off road parking. A developer wouldn't spend more on a renovation than they could recoup back on the sale. A friend had 2 electronic operated velux windows with rain sensors put in for their extension and they have never used them! As for their bi fold doors they have banned their children from using them! ( at a recent children's party, granny was in charge of opening and closing doors to let the kids in and out!) Their five grand door is too precious to be even used.