Day of the Cockroach, by Steve Lyons, is a classic base-under-siege story, the sub-genre that Lyons has made his own. It has the Doctor, Amy and Rory arriving in England in the immediate aftermath of a 1980s nuclear war, or so it seems; an idea used about the same time by Big Finish in Protect and Survive. It's fairly obvious from an early stage how things will work out, but Lyons has a very competent style and Arthur Darvill does a decent effort at the other characters' voices.
The Nu-Humans by Cavan Scott and Mark Wright is the most sfnally adventurous of these stories, set on a planet with very high gravity (why do sf writers so rarely do that?) and with the eponymous Nu-Humans having a very similar history to the Cybermen, only less boring. It's a bit gory for younger fans but firmly recommended for older listeners, including those who are not really into Who. Read very well by Raquel Cassidy, who seems to have a real knock for this.
Raquel Cassidy also reads Simon Guerrier's The Empty House, which is basically a ghost story with a Whovian/sfnal twist; it's rare for me to feel this about a single-CD story lasting little more than an hour, but I felt it actually could have been shorter. Still, it would be suitable Halloween fare for Who fans of all ages.