It's dog-eat-dog in the insurance world these days. Your renewal notice is no more than an offer to re insure - accept it if you wish, but anyone doing so without checking the market is a fool, TBH. The insurance companies have no loyalty to you any more, sadly , and you owe nothing to them.
Use at least one comparison site, then if you feel you wish to stick with your original company, then give them the opportuniity to offer a new quote - or simply go elsewhere.
I stuck for years with Direct Line, and very good they were too, but suddenly, their premiums became unrealistic - so I swapped. I'm currently with the Club's insurers and happily so, but will change quite readily if the need arises.