Check the price of third party insurance, these days it can cost as much as comprehensive. Worth checking out though.
If you had an accident and your car was written off the insurance would pay you the market value of your car if you have fully comp cover - which could be more than you expect because of the current shortage of new cars.
If the accident is your fault and you cause third party damage to other vehicles, property or injure people the pay out to them will be the same regardless of your type of cover.
I suggest you look at 'webuyanycar.com' for an instant valuation of your car (be brutally honest about the mileage and condition) and add 20% on to the value they give you to get a rough idea of how much the insurance would pay out if your car were written off today.
Use this site for third party insurance quotes
https://www.comparethemarket.com/car-insurance/third-party/
When you have all that information you will be in a better position to make a decision.