Adrian

Whist not wishing to comment on the efficacy of any immigration rules, I would say that it is incumbent on anyone wishing to enter any country to be clear what are the current rules of entry.

I would also suggest that most people in the UK (or any other country) do not need to know, or to be told as a matter of course, what special conditions might apply to foreign nationals. In the case of venues who do book foreign acts, then you might expect them to do some research but the ultimate responsibility lies with the in-coming artist or his/her agents.