Rover 200 engine hunting/misfire at idle

At idle the engine seems to be hunting for the correct RPM and jumps up and down on the rev counter, this was a minor problem that occured sometimes and now its all the time sometimes the engine cuts out. It is ok when you hit the accelerator and hold at anything above idle revs, and when driving it seems ok, sometimes when you put your foot down it seems to misfire and judder quite severely. I checked the Turbo and EGR valve, all seems ok. I've been told its most likely the Crank Position sensor.

Here is a link to a video i took http://www.youtube.com/watch?v=RBsG996vVvY&feature=youtu.be