In my club we have UV lights at all tills. Anyone caught with fake notes is detained by our "gentle" door staff and the police are always called.

One guy didnt even make in into the place 2 weeks ago as he was searched and had nearly 800 quid in fake twenties. !!!!
It took 4 door men to escort him to the office...LOL

There are some really good fakes out there now. We have a sample that looks and feels exactly like a real twenty even has a proper weaved foil strip. Fails the UV test though !