The one thing to remember is it is policed by complaint.

If nobody complains, then nobody is prosecuted.

Obviously it is a bit risky, but in my experience nobody is prosecuted on the first complaint, anyway - the Police visit the licensee and explain that 'a complaint has been made, so please toe the line...'

My 'experience' goes back over thirty years, during which time nobody was prosecuted, although three licensees were given friendly warnings.

There was an exception, however - one pub had a next door neighbour with a grudge, and the Environmental Health department were called in to take audio level readings. Although it never came to a prosecution, the ill feeling killed off the sessions.

Hope that helps...