Scenic clutch bleeding problem

Help please, I've just replaced the clutch on my 2004 1.9 dci Scenic with a single mass kit but cannot get the clutch to bleed properly. I initially bled it using a syringe and drew the fluid through the slave bleed nipple. I tried to start the engine a few hours later. But the pedal went to the floor. I have tried forcing the fluid back through the resevoir from the nipple and power bled it twice but every time the pedal is spongy after a few hours or overnight. There is no signs of leaks at the M/cylinder but what is the best way to bleed it? It seems to me that is where the problem lies.
Any suggestions would be much appreciated
Dave

Scenic clutch bleeding problem