Different Clutch Problem On I10

Hi i'm just wondering if anyone can help me.

I have an i10 which was only purcshaed as new in july 2009 and was serviced in july 2010. I have now developed a problem with the clutch judderring. THis mainly happens when the car has been at speed for a period of around 30 mins, when the car goes into 1st gear the car will judder, however this is an intermeintent fault. The car has been to the gaarge on 3 occassions and on all three occassion the garage can not reproduce the fault, and they will not look at the clutch due to the time it takes, they only option they are offering me is to take them for a drive in the car with or them to keep the car to drive it. Both of which are good ideas, but as the fault is intermentinet it is not gaurrented to produce the fault with them. They have also suggested i bring it when the fault occurs, but like i keep trying to tell them this is not possible as it will judder in 1st gear and then it will be fine.

The problem is not just my driving either. Any help on the problem will be greatly apperactited.