Milnerton Nissan selling un-roadworthy vehicles

In January I was looking to buy another vehicle. I came across 2 vehicles on Milnerton Nissan's page which I was interested in. Upon enquiry, the salesman, Mike, told me that the two vehicles I was interested in were "special condition" vehicles and he would not recommend that I buy it. Instead he offered me something else. I sent to test drive the vehicle which still looked in good shape. He told me that only the tyres are a bit too big and that they scratch against the vendor upon turning. I test drove the car and heard it but thought that I would anyway change the tyres. I told him I was happy and that I would like to buy the car. On 14 January I paid cash for the car. I sent to collect the car to sign the documentation. Upon signature the salesman affixed a stamp to the contract stating that it was a "special condition" car, after I had already paid. He also gave me the car without a license disk, number plates and a road worthy and told me that I can do the change of ownership on my own or they will charge me R4500 to do it. I opted to do it on my own. After a fee days one of the tyres started to deflate. I called Mike and told him I was not happy with the car and that I want to return it and he said I cannot as it is a "special condition" car. I went to fix the one tyre that kept on deflating and the garage told me that the chassis is bent and the wishbone has been replaced and that is the reason for the tyres that scratch. I demand a full refund of all monies paid to Milnerton Nissan. I will be taking my car to them tomorroe and will not leave until I get my money back. I am driving with 3 children in the car on a daily basis and our lives are at risk.