Just adding another factor into the mix.....
As valid ATCO's in the UK, most airlines provided a famil system pre 9-11. This has all but finished now due to the security rules currently being experienced, this is despite all ATCO's employed by NATS requiring home office security clearance as a pre-requisite of employment.
Unofficial visits were also enjoyed and it gave us an opportunity to talk to the customers properly instead of barking out instructions ten to the dozen.
I know that most of my colleagues will agree that we have lost an invaluable source of feedback and enquiries that looks unlikely to return.
My thanks to those who may have entertained our intrusions in the past.