Cobwebs is a good start to this mini-season. The set-up is decently spooky: the Doctor, Tegan and Turlough encounter Nyssa - for whom many years have elapsed since she left the Tardis - on a deserted space station filled with, well, cobwebs, also robots and a deranged computer. The plot develops into a tale of cures for space plague and temporal paradoxes, and impressively manages to wrench two of the three cliff-hangers from what is apparently the same situation viewed from different time periods. I wasn't quite sure that the temporal paradox was satisfactory in the end - to what extent did the Doctor cause his own involvement in the situation? - but perhaps this will be resolved in the two sequels - the loose ends here seem to indicate that the three stories will be linked.
What makes it of course is that the core cast are obviously having a whale of a time getting back into the spirit of '83. Tegan if anything is more spiky than I remember her - did she ever have a go at Nyssa in the original series? She lets fly at everyone here. Of the cast of creepy scientists and others, Raymond Coulthart stands out as the various artificial intelligences, though the other guest cast (all moderately well-known actors) are decent as well.
After the increasingly fannish progression of the last mini-season (Legend of the Cybermen would be pretty impenetrable to listeners who had not seen a particular Second Doctor story, though very enjoyable to those in the know) I'm glad to say that Cobwebs would probably be accessible to listeners with only a vague knowledge of Who (basically, that it's about this guy who travels in time), and probably a good starting point for Big Finish newbies. Recommended.