I know insurance companies are risk based, but in the years when you don't claim, and assuming you have the maximum nbc the premiums do not still come down, so the company is effectively making a profit from you.
Then, when you do have a claim, or as the OP has several in quick succession although they pay out, they then start to recoup there losses so they are having it both ways by making money when no claims and recouping the money with higher premiums when they pay out.
I imagine that the cost of one claim can take out many years of premiums, the most expensive I was involved in cost well in excess of £30,000 in total.
Just had my insurance renewal through to day, at just under £8 a week it seems good value.