Hi janeio,
This must be difficult for you.
If he's not contributing to the mortgage, then being blunt, if he was dead you wouldn't be any worse off, as you'd still have to pay the mortgage as you are now. On the other hand, if he died at the moment, the policy would clear off the mortgage for you.
If your lender didn't take an assignment over the life assurance policy, then you can cancel it at any time. Although strictly speaking you need both signatures to cancel a policy, if you simply cancel the Direct Debit, the policy will lapse anyway. You could replace it with a policy on your own life. (Make sure cover is in place on yourself before cancelling the other one.) I'd suggest you then write to the lender and explain to them what you've done and write to your husband advising him what you've done and advising him to take out and pay for his own cover if he wants it. If the lender wants cover on your husband, they can pursue him to take it out.
This is a possible solution off the top of my head. You should run it by your solicitor before acting on it - I'm not a solicitor.