are you sure it's bleeded 100% and no air trapped somewhere?
I've fitted the same kit from Martin and not a problem at all.
Had the car on 2 post lift with someone behind the wheel pressing the clutch, while I was opening/closing the bleed screw at the gearbox and keeping the fluid level up.
Also check how the slave cylinder is fitted on the box, as far as I remember the bleeding screw needs to point down below when fitted instead of up, because you can fit it both ways!

Stephan