i had this problem, searched this forum and from 2005 found a thread that helped me. a woman found her hubby was driving her car without waiting for all the light thiggys to go out. As my car only did this when my hubby drove i corrected him and she has driven fine since.
Then 3 weeks ago it started doing exactly the same as yours. I just disconnected the battery (as i was a long way from home with the children). it's a bit like rebooting a computer! It stopped over revving and has driven fine ever since.
The only real way to find out the problem is to have a disgnositac machine put on it. that is the general opinion on the forum. I have managed to get away with "rebooting" till now.
hope you find the problem was the simple as mine!
x