Brand Management by Christopher Cooper was my favourite of the three, with Benny landing on the world of Lyndyaz and encountering a culture where she is worshipped as a goddess. Anjli Mohindra, who played Rani on the Sarah Jane Adventures, turns up as one of a pair of evil siblings who are running the place, and there are lots of larks involving archaeology and explosions.
Bad Habits, by Paul Morris and Simon Barnard, continues the religious theme with Benny and Ruth going undercover as nuns in an order run by Jacqueline King (who played Donna's mother on TV Who) in order to get close to a vital relic. I went to a convent school so have heard all the nun jokes before, and several plot elements are wildly implausible even by the standards of Doctor Who spinoff stories, but at least everyone seems to be having fun.
Despite its title, Paradise Frost has no religious content, but instead features Benny, Ruth and their obnoxious pilot trying to solve the mystery of a frozen former resort with only three vaguely human inhabitants, of whom the most mysterious is played by Arthur Darville (Rory on TV Who) and the most evil by the ever-luscious tones of India Fisher (former audio companion Charley Pollard). There are also loads of sandroaches. I can't remember another audio with both Bowerman and Fisher, and they spark off each other beautifully, but I felt the means and motivation of Fisher's character didn't quite hold together. And then the last scene, where the main story is over and Benny reaches her destination, is basically an extended trailer for the next series. Which I look forward to.