Self-contained from the late '70s/early '80s, possibly part of the BBC's Schools and Colleges programming.
A group of four(?) children is engaged in a battle-of-wits with two disembodied heads communicating with them via a television. Outwitted, the two heads (one male, one female?) agree to releasing the children from the room they've been trapped in --
-- Except there's a twist-ending. Buggered if I can remember what but I think it implied the kids were trapped unwittingly in the same, never-ending battle of wits.
I caught a lunchtime repeat of it a few years after I first saw it and seem to remember one if not both heads were played by faces familiar from . . . uh, something else.
SOunds like a Dramorama?
Fairly sure it was on BBC 2, so it wouldn't be DRAMARAMA.
It wasn't one of those crappy stories from Words and Pictures was it?
I vaguely remember on of those that had a blue alien kid in it.
V
There wasn't any intercutting with yer man Wordy, so no. Nor at any point did the likes of Brian Cant, Lesley Judd, Fred Harris, or Derek Griffiths interrupt with something educational. Probably only ten-fifteen minutes long (can't imagine it would've been a full half hour).
A chum of mine who's a few years younger asked if I remembered it which I did as soon as he mentioned the disembodied heads. So I'm guessing it must've been repeated after I last saw it (early '80s, I think).