What are these batteries used for?

Apparently for emergency back-up lighting. I found a website about a Scottish cinema which used that system too. Where is the Coronet cinema which you photographed? It looks interesting.

As the other answer note, they're for emergency power. There are 24 batteries if I counted right. They're be separate, 2 volt cells, wired in series, providing 48 volts. They were more than likely wired to emergency lights to provide illumination so people could see to get out of the theater in the event of a commercial power loss.
The batteries would be ruined by now unless they still had a functioning charger connected to them. If batteries like this aren't kept charged, they sulfate and can no longer be charged or used. There could be some scrap lead value in them. It depends on the market. They should be disposed of properly in any case.

Lead acid back up batteries for emergency lighting,Probably flat by now.

Lead acid back up batteries for emergency lighting,Probably flat by now.

Lead acid back up batteries for emergency lighting,Probably flat by now.

Lead acid back up batteries for emergency lighting,Probably flat by now.