Hello Catherine, when you say ‘abandoned’, has the resident left and asked you to store the items or are they no longer needed?
It ought to be the responsibility of the resident / their next of kin to empty the property.
If the resident has died, we usually make it clear to the family that they will continue to be charged until it is cleared, or mostly so.
We recommended house clearance, Emmaus, British Heart Foundation etc.
House clearance comes with a cost which the charity ought not to be responsible for.
If the goods have been abandoned, I suggest you notify the resident / family of a deadline by which it needs to be cleared or else it will be given away.