Thought I would post back as you're car had very similar symptoms to mine. My car, it turns out, had a cracked exhaust valve with two small bits missing. Therefore it essentially was running as a three cylinder, hence the juddering and stuttering and I assume the over revving was the ECU trying to sort things out. Changed the head at the weekend and it is now lovely and smooth. I still don't think I've gotten fully to the bottom of things as it still whiffs a bit of petrol. But what a difference. I would suggest you try a compression test - if you still have the car.