Auto Magic refuses to accept responsibility for their poor workmanship r

I had a minor repair done to the front left fender by Auto Magic as appointed by Auto and General, my insurers. The repair was done with little hassle. That is the good part. A week after the repair it rained and the left front cabin filled up with rain water. My daughter took the car back and they fobbed her off saying it couldn't be their fault. So I took it back a day later and Mark gave me a story that it was impossible for the leak to be caused by them as the fender is not part of the watertightness of the car and that it must be leaves blocking the air vent drain holes. He sent me away to attend to it myself. Well I found that under the bonnet there was one fender bolt that was totally loose and another completely missing. The missing bolt was at the bottom corner of the windscreen and the bolt hole let all the rain from the windscreen directly into the cabin over some electronic boxes. When I phone Mark of Auto Magic he apologised but offered no service to correct the defect, check for other poor workmanship or offer to dry the car out. My call was then cut off. It took me a week to dry the interior with an wet vacuum and a dehumidifier and many hours of my time lifting carpets and removing panelling inside the car. I have subsequently replaced the missing bolt and tightened the other. I wonder what else will be found wrong in time. I hope the electronics do not fail due to Auto Magics poor workmanship.