Hello vernon.
You say your car insurance premium has doubled- is that also because of this issue with the cat?
How material was the information about the cat to your claim? If the policy only covered cats up to age 7, for example and yours was 8 but you said it was 7 then I can see why they cancelled it, but in other circumstances it could seem a little harsh.
I expect that the house insurance proposal asked whether you had ever been declined/ had cancelled any insurance, not just house insurance, but check the wording