Vehicle repairs not satisfactory

My vehicle was sent to this company by my insurers, Budget Insurance, after an accident that was caused by another vehicle not stopping at a red traffic light. My car's bumper was badly damaged and this company had to repair it. Bad bad bad service. Hardly any feedback, taking SIX weeks to repair the bumper and promises made without much happening. It took me and my son to DRIVE to this company to try and get hold of my vehicle and sit there for 3 hours while they ****pered about, trying to finish what they were supposed to do. They removed the left-hand wheel well cover and the privacy cover of the boot of the vehicle and now, three weeks later, still haven't returned our property - they "lost" it. Not recommended at all.