If you are involved in an accident, and you only have third party cover, then it will only be your passengers that are covered, and not your car. If however you can prove it was not your fault, then you can claim from the persons insurance who was at fault. If you have comprehensive insurance, your car and passengers will be covered, however this is not likely to be for more than £4000 for personal injury insurance.
If you are in a crash, then you must stop the car and keep calm. It is law in the UK that it is reported to the police within 4 hours. It can also be useful to try to get a witness. You should also exchange insurance details and personal details, and also note the car registration number. You should then contact your insurance company as soon as possible.
Even if you think you are to blame for the accident, you should not admit this till you have spoken to your insurance company.