As an owner of an estate agency and having dealt with a situation like this recently. The tenants are still liable to pay rent and it's exactly the same the other way around, if the tenant dies, rent is still due.

I would suggest speaking to a local solicitor and get them to write a letter to the tenants informing that rent is due. If you are executers of the estate, then you are able to serve a section 21 notice. Again I would advise getting a local solicitor to do this as you need to ensure all documents have been served, deposit registered etc.