its idiot tax. the insurance companies increase your premiums each year for loyal customers. they do rough calcs based on your risk and likely hood on how much extra you might pay, they then charge you that. if you take that premium and just pay it with out looking round or calling them the next year they add more. till a point you either say too expensive and you either go elsewhere or ring them and then they do you an "amazing deal"
But obviously insurance will go up for legit reason too. i.e. tax that the goverment take goes up, area risk, vehical risk (have baywindows been stolen more in the last months) personal risk (if you made claims, your likely hood to claim, credit history etc etc) so somewhere inbetween would be a good start for something realistic you should expect to pay especially if you have not had any changes in personal circumstances