You might want to edit the title of your post as I think what you are talking about is mortgage repayment protection insurance?
You would need to check your policy documents to see if it says anyhting about you having to make efforts to get back to work.
On whether you should cancel the policy, check whether you could make another claim and if so, for what. For example, if you were made redundant again in the future (hopefully not!) would you be able to claim for redundancy again? Or would you only be able to claim for other reasons.......