Since when?
Its the driver who builds the no claims not the car!!!

If you havn't bought the porsche yet then simple answer is don't buy a porsche, buy a car your insurance company won't screw you over with. Thought you were after a diesel anyway thats cheap for parts??

PS. No insurance company is going to want to insure you on a 3.2ltr porsche immediately after you've crashed a 1.8ltr skoda, especially if the accident has been deemed your fault.

Do you have any evidence to argue your inocence such as oil spill on the road or was it just wet?