Accident on company's insurance policy, do I need to disclose this for personal car insurance?

Unfortunately, yes! You will have to disclose this when looking for car insurance as it was you who was driving and it was your fault. As with all policies, omitting this information will invalidate your car insurance when the time comes for you to make a claim. The insurance company will know that you had an accident that you did not tell them as that becomes the basis for nullifying your policy, leaving you liable for damages.