I believe you CAN do supply teaching as an NQT now. My neighbour could not get a full time post and has been told that if she does REGULAR supply it can count as her probationary year. If she does it part time, however, she will take longer to complete her 'year'.
I'm a bit puzzled about all this. I thought teacher training these days included a lot of school based training, ie doing the job. If that's so, it should, at least in theory, weed out the trainees who are not going to make it at an early stage. How is it this NQT got as far as she did and found the job was not for her?