Have a search through the insurance section of Askaboutmoney as there's plenty of threads there suggesting places to go for good deals on property insurance.
You're correct in assuming that your Mortgage Repayment Protection cover will not pay out a redundancy claim as you voluntarily left a job. However, before cancelling, consider that this policy presumably also covers you in the event of ill health, which you'd be losing if you gave it up. You might want to check if you can continue the ill-health cover at a lower cost.