Got problem with clutch in that the clutch pedal goes harder when the car is ticking over, and then when go to drive off it slips!! but after a while of using the clutch it goes back to normal and the clutch wont slip..
So had a new uprated clutch fitted and still got the same problem when the car is ticking over or going down the motorway when the clutch is not being used, the pedal goes harder again!!!
Any ideas???????

 

Sounds like a faulty slave cylinder and/or release bearing.

Rob