2013 Opel Astra 1.6Essentia bought asa demo in2014

I bought a 2013 Opel Astra sedan as a demo model during April/May 2014 with -+14000kms and in less than a year and 15000kms later the clutch starts shuddering after its 30000km service at Barloworld Zambezi where I bought the car. I complained about the clutch shuddering 2 weeks after the service I am told it is my fault and I am to pay R15000.00 to replace the clutch. After complaining to General Motors SA warranty section in Woodmead I am told it is not covered by warranty and I have to pay the R15000.00 to repair it. No concessions will be made although I was driving the car for less than a year and costing me R200000.00 as a demo model that was previously driven by Barloworld staff members before I purchased it last year. To me who has been a loyal Opel, Chevrolet and Isuzu owner over the past 40 years this is a low blow to have a demo model Opel Astra sedan's clutch giving in in such a short space of time. I am a qualified motor mechanic that served my apprenticeship at GMSA in PE and to me this smacks of weak quality material and fitted parts which GMSA won't admit to and rather telling me that they will negotiate a R2000.00 repair and replace discount with Barloworld Zambezi