Poor and shoddy workmanship

After my car, a Volkswagen Polo was at Manimachs Gansbaai for weeks from the 27th of May to the 18th of June for a replacement head gasket when I received my car back and drove home ( 120km) it was idling unevenly and stuttering all the way. On our arrival home I immediately wrote a mail to inform them that there was a problem with my car. The car also had no power. I took it back and was told by the machanic the the system just had to be "burned" clean. Now just oven 1000km later (of which 360 km was driven to get the car back to the garage to be told the system needs to be driven to get clean) the head gasket again blew and according to the engineer now looking at it, the stutter was because Manimachs never set the timing right in the first place, after they worked on the car. I contacted Manimachs about this because I feel I paid for a vehicle that was not fixed and I demand to get my money back, so I can at least pay part of the other mechanic's fees. Manimachs had their lawyer send me a mail that I should not have driven 1000km with the car but I fail to see what more I could do but take it back to them...which I did and still it was not fixed. I feel that I should get more out of an R8460,00 mechanical job than just over 1000km and therefor my poor rating.