Hello I am a solicitor with over 15 years experience. I will try to help you with this.
This will depend. In some circumstances it is possible to change the beneficiary and he may have done that. What you describe doe snot sound alike a life insurance policy. A life insurance policy would normally pay out money on the insured person dying and pay that money to the beneficiary. Where people buy property jointly this is usually to ensure that the survivor can afford to pay the motgage. This type of policy may have clause making the identity of the beneficiary irrevocable. Do you have a copy of the policy document. Also do you know if you hold the property as tenants in common or as joint tenants? This should have been made clear at the time of the purchase.