Sold me a damaged, abused, leaky vehicle and delaership refuses to cancel deal

On Friday the 6th of October I collected my 'new to me' 2016 Chev Corsa utility with +-34000km on the clock. The Whatsapps exchanged between the Salesperson and me indicated the vehicle is "100% clean" and has undergone their 101 point "quality check" and a dekra roadworthy. I checked the vehicle the day before in the workshop where they were "sweetening the deal" with smash and grab tinting. Initial checks showed the car was in a good condition but the problems started immediately after collection. The vehicles gears ground all the way home, I was thinking because of the low mileage it may still need to bed in or something, so I drove around very slowly. When I got home, very proud of my clean, one owner car that I bought I found there was silicon on the roof of the car where the fittings were sealed, not done very nicely, so I cleaned it up and never thought twice of it. The next Monday after work I was parked at class where the late afternoon sun shone on the right side of the car for the first time that I noticed and I went cold with what I saw, there was bodywork done on this vehicle from the back by the petrol cap, right to the front bumper and overspray present on the quarter window's seal, the roof, the inside of the door cavity, the front bumper was also sprayed. The next morning I took the vehicle back to the dealer where I spoke with Mauritz (the used sales manager) who quickly dismissed the damages as cosmetic and explained that the previous owner had a canopy that scratched the car. He refused to cancel the deal although the bank gave me permission to do so and this is where the trouble started. He said if I can't prove the vehicle was in an accident, I have to accept it as cosmetic repairs. The damages aren't quite as simple as that, there's sandpaper marks under the paint on the entire right hand side, almost halfway down the car (not just a touch up in my view), I decided to go see an accident assessor to guage the condition of the car as Mauritz insists they will not send my vehicle for a quality check at Dekra and the R2000 fee will be for my account, the findings were not good, the guy checking the car says the entire panel will have to be taken down to bare metal and resprayed. He also found dents on the roof with swirl marks around where they tried to clean it up. Thereafter he pointed out that the engine has alot of old oil on it and we climbed under the car to see that the car is leaking quite a bit of oil, he pointed out rag marks where someone had tried to wipe away old oil to clean it up and this was covered by the new oil in the area. He then measured the tyres and pointed out that the spare wheel is ******* as the tyre only has legal tread in the middle. He referred me to Dekra centurion and I called them and took the car through. On the phone and personally they said I shouldn't waste my time trying a roadworthy as it will fail simply on the oily engine and the spare wheel isn't helping the chances either, so I left it. My question now is, how am I expected to trust the 101 point quality check and the apparent roadworthy if everything else points out that this vehicle is in fact unroadworthy, then why am I not allowed to exercise my right to return the vehicle and cancel the deal when there is clear evidence that there are damages on the vehicle that I was not shown by the dealership and evidence now points out that some damages were deliberately concealed. Mauritz proudly advised me he himself puts the vehicles on a lift and checks them for quality, how does this professional miss an undercarriage full of oil? I have been advised to take this further, I'm not sure how though, as every complaint is countered by an improfessional email telling me I bought the vehicle as it is and must accept it. I'll be clear, I WILL NEVER BUY A VEHICLE THAT HAS HAD SPRAY WORK, I should have been told about the damages, I should have been told this vehicle used to be a fleet rental vehicle and not a "One owner" vehicle. Had i known this, there would never have been a deal in the first place.