You be the judge ... gross incompetence or *****?

Took my Jaguar F-Pace in for a service at Jaguar Landrover Bryanston after expiry of 100,000km service plan. I complained of a slow water leak and intermittent lag when accelerating. They sent me an email detailing a service and repair cost of more than R50,000. The intermittent lag issue was not addressed in the quote. I went through the quote and managed to reduce it to R18,000 (by deciding to repair rather than replace the auxi****y radiator, and by omitting various other things). They called me the next day and told me that they had done a "block test" which showed that the head gasket had failed and exhaust fumes were mixing with coolant. They would have to replace the engine which would have been damaged beyond repair by the leaking gasket! Catastrophic failure (seizing of the engine) was imminent. When I refused to accept their opinion they sent me a video demonstrating the block test and proving that the head gasket had failed. I told them not to do anything and collected the car, paying the R18,000. The following day I drove the car to a Jaguar specific expert mechanic, explained what had happened, showed him the video and asked him to investigate. He phoned me in less than an hour saying there was absolutely nothing wrong with my car and I could come and collect it without charge (even though they had conducted tests to check the integrity of the head gasket). I have since driven more than 5000km (long trips, short trips) without any hint of a problem. Had I accepted the advice from Jaguar Bryanston I would have been in for a bill of somewhere around R300,000 and they would have had a perfectly good second-hand engine to sell.