Just to dig this thread up again - I recommend, to all who like the TV show: Get the audio adventures by Big Finish! They got special deals when you buy the whole season. I got all three seasons now. Haven't listened to the third one, yet, cos I KNOW I'll totally get wrapped up in S&S again as soon as I do and that's not supposed to happen since I got other things to do, right now.
Susannah Harker and David Warner are awesome as Sapphire and Steel. Believe it or not. I didn't when I first came across the audio adventures, giving those two an almost Joanna-like sneer. But they do capture the essence of the characters perfectly. In fact, you might find their versions slightly more likeable than the TV-versions - especially Steel who's still his grouchy self and still can be a bastard but he does seem to care more about Sapphire. There's also several appearances by Silver, too - hooray! And there's other elements: Gold and Ruby. The stories are very interesting and as far as I'm concerned, really addictive. And that's from someone who usually doesn't like audio adventures.
I still recommend buying them directly of Big Finish (since rising sales numbers MIGHT just entice them to do a fourth season ... ;)) but if you want them cheaper, some can also be found on ebay (not sure if they're all out there).
PLUS: For all of you who didn't like the end of Assignment 6 - the audio adventures are set AFTER Assignment 6, actually all taking part some time around the year 2000, as far as I remember. So they got out of the cafe somehow. It's never mentioned how. I got the impression, though, Silver might have had a hand in it ... :)
So - top marks from me! But I'd like to hear what you think of the lot. *wink, wink, nudge, nudge* ;)