According to Play.com Thief of Time
, The Truth
, and Carpe Jugulum
were supposed to be released on June 30th. It seems you can preorder from there.
The Fifth Elephant
seems to be available now.
Personally I disagree with you about Stephen Briggs and think that Tony Robinson is awful at reading the books - but that's just down to personal preferrence. I'd actually prefer to read the books - I can do my own voices then.
The BBC in their shortsightedness never seem to make these plays available to buy. I have also enjoyed all the radio adaptations of the books. But that's the BEEB for you.
“Men never commit evil so fully and joyfully as when they do it for religious convictions.” – Blaise Pascal