Hi mate, ours has got similar probs and I think I might have found the cause for the jerking.... If anything like ours, it was jerking pretty and I discovered that the diesel was picking up a lot of air bubbles (fuel starvation casuing jerking?)
Anyways, found that priming the diesel pump made it drive better and concluded that the primer was faulty, letting air in (these apparently are common problems and the insides of these perish).
Anyhow, changed it but not been able to drive it much due the clutch cylinders needing replacing, but initially it does seem to have done the trick.
Basically (if you do a search on here, you'll see I've been messing around with the EGR valve and bust the pipe!) a new EGR valve, new EGR pipe and it's running sweet as a nut.
You won't need the pipe, so just get the EGR valve. If you got the G8T engine, buy the valve from GSF parts - it's £65 plus VAT (it's listed for the Laguna with the G8T engine, so its the same). Buy new gaskets from the dealers as they don't come it (you need 2 at about £3.50 each).
I Had to buy the EGR valve from the dealers at £120 plus VAT as they wouldn't sell the EGR pipe to me without it (game me some excuse about the unit being modified / sold as a single unit!)
I must stress though, it was only fitted a few days ago and the car hasn't been driven much since then, but even in the short time driving it, it feels different - more lively, more torquey... and it passed the MOT today!