Well spotted ... those are badminton lines on the floor. The hall was multi-purpose, the stage had a full below-stage area and dressing room, and there was a projectionist's room above and behind. No doubt they had dances there as well.
The asylum was founded in 1900 and closed in 2000. It was built to house between 300 and 400 patients. It is now being redeveloped as a business park. If you look at the other shots, you'll see that the place is gradually being gutted after some years of being abandoned.