It is hot and stuffy inside Ann Coffey’s Westminster office and the MP has been talking non-stop for 70 minutes without any sign of flagging. That’s quite surprising because Coffey, who recently quit Labour for the newly created Independent Group (which has applied to become a political party called Change UK) is not fizzing with vote-catching proposals. She is the spokeswoman for children and education, but if she were to become education secretary tomorrow, she would not change the system.…