Even where those intending to open schools have no such ambitions I have little faith in the ability of parents, charities and even some teachers to give children a comprehensive education without a governing body inplace to ensure that basic minumum standards are met.
I don't know much detail about these schools, but I don't think they'll be allowed complete freedom with the curriculum. Furthermore, I'm sure that they will still be subject to government inspections to ensure they meet certain standards.
My understanding is that they will have some freedom of curriculum, and the main difference is that they won't be under local government control. Whether that's good or bad I don't really know.
I'm naturally concerned that religious and particularly creationist groups might try and influence the curriculum, but what does it say about all other types of groups, including industry and science foundations, that they don't seem to be interested in education - or are they?