Recently Brian suggested we cover their full run of Sapphire and Steel dramas for British Invaders and they were really fantastic. David Warner and Susannah Harker are both fantastic in the title roles. There's plenty of good spooky stories and the whole cast, production and sound design are just very well done.
I haven't listened to as much Big Finish as I would like to but what I have done has all been terrific. If only time and money were no object. Anyway my favourite spin off from a British Invaders show is the Big Finish Sapphire and Steel audios.