Lost Baggage Questiion

On a direct 2 hour evening flight from Spain to London, Britannia Airways
lost my bag. They offered no assistance at all in obtaining any necessary
replacement items and wanted to put the whole thing off on their contract
baggage service. The baggage service in turn said it was the airline's
responsibility. I was leaving the next day for France and spent 5
miserable days there with no bag. I was not contacted at my hotel in Paris
concerning the bag but the baggage service did have it when i got back to
London.

Does anyone know for sure what the rules are concerning lost bags and the
airlines responsibility in assisting someone in a situation like this?
Thanks for any replies.

Eric