A Legal Question if anyone knows about CCTV

[Finbar]

Help legal eagle friends! My former place of employment ( a restaurant ) has decided to do something that I think is illegal. I know this because my former staff has called me to gripe to me. They are still loyal to me. They have put in a camera, one of those little half globe black glass ones, into the bar at the restaurant. They say it is because people are stealing. It supposedly is transmitted to Corporate security and stored there in case it is needed for review.
Herein lies my problem with this. There are no signs posted for employees or customers that say that the location is being monitored by CCTV. I also know this company, and they are way too cheap to spend money like this over a missing bottle of Abslout Peach. So, are they dummy cameras to scare the staff? Or are they real? If they are real.. does anybody know the legality of this? I researched a little bit tonight about the Data Protection Act of 1998, but it is mostly about the employees, not the customers. Any advice would help.