Engine Lumpy when starting from cold

I fitted a new cylinder head on my TD5 due to Diesel in the oil last November. Ever since then, when I start it in the morning, it runs really lumpy just for a few seconds, like it is only firing on 2 cylinders. Then it bursts into life and is fine from then on. I've fitted new genuine LR glow plugs, but that made no difference.
Any suggestion please.

fuel running back ?

check the FPR(fuel pressure regulator... it's fitted where the 5'th glowplug must be... just in case u dont already know that)....if u see diesel around it this might be the problem.