Thanks for you comments. I own the lease so I am an owner occupier, not a tenant. The freeholder is responsible for maintenance of the fabric of the building as set out in the lease agreement.
I do have contents insurance but as the incident was due to neglect of maintenance on the part of the freeholder then I'm not covered. If this had been due to a burst pipe or a storm blowing of the roof then it would be covered. If my insurer covered this then they would be, in effect, covering another party's neglect of duty. I can't imagine that any contents policy would cover the policy hold