I'm annoyed. I can't go to the Kings College Greek play next week, They're performing Lysistrata, as part of the University of London Festival of Greek Drama, the only production of the festival to be performed in Greek.
I have been to the triennial Cambridge Greek play, Medea in 2007; I missed the Oxford one last year, Agamemnon. As far as I can tell these are the only regular productions in the country. The excellent database of the Archive of Performances of Greek and Roman Drama (APGRD) at Oxford doesn't support searching by language of performance at the moment, though I'm pleased to learn that it's an enhancement they might consider.
I imagine that only a university would have the resources to put on such a production these days. While my school might have managed it in W H D Rouse's day, bringing together Caldwell-Cook's Mummery tradition and the school and Rouse's early pioneering of the direct method in language teaching, by the time I was in the sixth form in 1971-3 there were only three boys in the Classical Sixth, so I doubt if finding enough boys to speak lines correctly in classical Greek would have been feasible, even for the small casts required by Greek drama. The school play was usually Elizabethan or Jacobean, usually Shakespeare but with Dekker and Marlowe added for variety. One year we performed Oedipus at Colonus, but in translation; I lurked in the back row of the chorus, singing the lines to music specially composed by Graham Sudbury, the music master.
Postscript: I see, through the ARLT website, that Oxford's Classics Outreach Programme have published a guide to Greek plays currently in production at http://www.classics.ox.ac.uk/outreach/theatre/index.asp.