While third party insurance is compulsory to take out before you can register your car each year, you can choose not to have third party property damage or comprehensive insurance.
If you didn’t have comprehensive insurance and you had an accident or your car was stolen, you’d need to pay for the repairs yourself, possibly to both cars, or purchase a new car from your own finances.
If you have had no significant driving accidents and the cost of comprehensive insurance is too expensive for your needs, you may instead consider third party property damage insurance. This provides a more limited cover than comprehensive insurance, as it is designed to cover damage to another car but not your own, but provides greater coverage than third party compulsory insurance alone.