Remember how insurance companies work .. it is all based on "risk" ... and by putting 19" wheels on you are increasing the risk... in their eyes... in 3 ways.
1) You have just declared yourself as part of the "chav" culture in their eyes .. you are now seen as a "boy racer" and are more likely to have an accident.
2) You have just made your car "pretty" and therefore a target for those malcontents who like damaging other peoples property, the chances of being keyed, for example, have risen.
3) Your car is now worth more to a thief, he can stell the car .. which is traceable, but remove the wheels and sell them as they are not.... so the risk of theft has increased.
Therefore they must decide, on the basis of risk, if they think it worth the "gamble" to insure you, and if so .. what "bet" (premium) they wish you to place.
You have your opinions and the ability to change company on your side .... they have masses of data and a clever computer system on theirs ..

It really is quite simple at the base level .... its a bet .. you bet you'll get damaged and need a repair .. they bet you won't and keep the premium..
