Once the insurance company "deems" your car is a write off, then NO, they cannot repair the vehicle.
The insurance company pays you for the value of your vehicle and then the insurance company owns it, which most sell to salvage yards for parts.
But if where you live, they allow you to keep the vehicle, then they usually "subtract" out salvage value of the value they offered you. Then you can take the money they offered (minus salvage) and have repairs done AT YOUR COST. You may also have other requirements needed, such as smog tests etc to have it registered for a salvage title, but the insurance company would explain what is needed.
I am confused about the 1100 pounds you quote on a premium. Is that a loan or the insurance?