In our experience, commercial vehicles and fleet policies have been especially hit with these increases. Insurers have quoted a general (not specific to individual clients) poor loss ratio on CV policies, not sure how true that is though..
Things that can help (some bit) to reduce the cost are: review the value of your van (remember insurers will not pay VAT if you are registered for VAT after a claim) and make sure it is correct. Remove any additional drivers you don't need (open drive is now an expensive option for most insurers, do you really need it?). Adding a spouse to your van may reduce the cost further. Make sure your insurer has your correct occupation noted as this can affect the premium a lot. Look at taking a higher excess.