I enquired about chipping my car and when I phoned my insurance co. they said they would no longer insure my car as it was classed as a mod to the car. There are other insurance companies however that will insure chipped cars. It also depends on the bhp improvement as to how much the insurance goes up. 0-10% would only cost me about 25
I have heard that insurance can be the deciding factor, I know of others who have been told by their insurance co. that after chipping they would not be insured. Not telling the insurance co. will of course invalidate your insurance.