Get a good lawyer to take up your case. From the facts you have disclosed, I would rate your chances of obtaining a judgment in your favour as "good", however, the only snag would be the quantification or assessment of damages.
But I didnt quite understand whether you were hit by a third party or otherwise as it would make a big difference on who to sue.
However, I assume that you are claiming on a comprehensive own-damage policy, and thus you are entitled to sue the workshop for negligence in discharging their duties, your insurance company for breach of comtract and negligence in restoring (as far as possible) your car to the original position prior to your accidnt, and you should be able to claim for damages based on the depreciated value of the car, mental anguish, and a BIGGER sum as a deterent to other shoddy workshops and insurance companies so that this WILL NOT HAPPEN again. In other words, you could be famous.
Btw - ths advise comes to you free (for now).
Best of luck!