You mean, there was actually more than one?
The one they showed on Danish television back in the 80's was the one starting with Blake suffering from amnesia, some freedom fighters then convince him that he is in fact the leader of the rebels, they flee, and somehow find this alien spaceship, that, after some time, suddenly tell them that it is going to self-destruct, and then does.... boom, end of story.
I was convinced that this was because the show did not have a large enough audience, and that it was just a way to terminate the show for good.
I think the series was actually called 'Terminate Blake's 7', come to think of it....
EDIT: Or 'Eliminate...'