Our insurance went up considerably also. We use a broker and I rang and asked why. They said it was the cheapest they could get. They got us two other quotes but both were more expensive.
I don’t think it is right that an insurer determines the value of a building. Has the insurer done a valuation? mostly we just find they increase the previous years value by a %.
To my knowledge insurers usually don’t physically value a building except in the case of a large claim.