Only on the radio, never been, but always worth a listen.
Also on my "to do" list.
In a separate but similar vein, the King's Singers were in Switzerland last weekend and we went. OK, it's a pretty new, purpose-designed concert hall in Luzern, not "just a church", but how just 6 blokes with no microphone assistance at all could make themselves heard so well - including hearing every word in the quiet bits - in a hall capable of seating, at a guess, over 1,000 people, speaks volumes both for their vocal skills and I guess for the acoustics of the venue.
If you like singing I'd highly recommend going to one of their concerts if you get the chance.
AES