If the house and mortgage are soley in your partners name and this was transferred over in the correct way (not as in the ex is about to go bankrupt and has only taken himself off the mortagage to avoid the creditors getting hold of the house) then I cannot see how his creditors would have a claim.
If his name is not on the deeds then the house doesnt belong to him and the creditors wouldnt have a claim.
If the ex is to remain on the either the deeds or the mortgage then the insurance would be a good idea.