As I said, I work in construction, so I cannot answer all of your questions. That said, over the last 20 years I have worked on 15-20 schemes ranging from £30m labour fflagship academies to the new conservative free schools. So that is me. You can draw your own conclusions if you think my opinion are valid.
is apparent that there is a huge lack of primary school spaces (in particular). We need to open schools by September this year to meet demand. Extending existing sites can create some capacity in some instances but not all and certainly not in the numbers required. If you ignore the free part, converting existing buildings will provide capacity quickly. They also have to meet new build standards.
Will answer your questions as best as I can
1) parents chose which school there child goes to
2) I'm not really qualified to answer this but all of teachers I have met are normal teachers not some two headed monsters
3) the funding model for new build elements are about 40% higher than refurb. So trying to increase capacity in existing schools would be that type of magnitude more expensive
4) pass-thats one for the government