For a long time landlords & agents have been unable to put a clause in a tenancy agreement stating that the tenant is responsible for maintaining solid fuel heating systems as this is described as AN unfair contract term (Office of fair trading 2005). So you cannot ASK your tenant to discharge your duty of care for you. (Unless a court order has been issued)
Should a chimney fire occur then many thousands of pounds could be lost in damage and loss of earning potential whilst the house is repaired. Not to mention any claim that a tenant may make.
If the landlord looks after a solid fuel appliance then they would have discharged their duty of care towards their tenants and would be keeping their own property safe from unnecessary fire risks and unwanted legal claims.
Remember as a landlord you have a legal duty of care to your tenant/s and as such blocked flues that subsequently cause death could result in the landlord being tried for criminal negligence or in extreme cases a manslaughter prosecution may arise