I must also admit to being the author of both "The Saga of Happy Valley" and the "Missing Cases". The latter were actually a series of fully authorised fanzines, produced in glossy magazine format with lots of original studio photographs, as an offshoot of Dave Rogers' Stay Tuned magazine. They were printed in Brisbane and sent out to subscribers world-wide at irregular intervals between 1989 and 1994. In all, there were four volumes, namely:

Vol.1 The Weather Merchants (1989) by Dave Rogers and Geoff Barlow
Vol.2 The Monster of the Moor (1990) by Geoff Barlow
Vol.3 Before the Mast.(1991). A Tara short story, produced only in photocopied supplement format
Vol.4 (1994). Contains 2 stories. Moonlight Express and The Spoilsports.

The stories in the first 2 volumes feature Steed and Emma Peel and are set in the 60's - same goes for Moonlight Express, while The Spoilsports features a team-up of all Steed's female associates, who come out of retirement in 1993 to do battle with 90's style diabolical masterminds.

Our review:
Well, Geoff is certainly a fan of the original series, something Don Macpherson (scriptwriter for the movie) could have benefitted from. Geoff know the background and the characters much better than he. Unfortunately, this doesn't exactly translate into world-shattering stories. Alright, the stories are good - plot, setting, etc. but they suffer from the curse of all fan-fiction (for that is what they are). Geoff is too close to his subject. Some of his descriptions of Mrs Peel are schoolboy crush material. Nonetheless, bar Patrick Macnee's Deadline, they are the best Avengers stories in the market place.
The prose is bolstered with some really quite fabulous black & white photographs from the original series (mostly from the Diana Rigg era, but a few others are interspersed throughout), and some somewhat dodgy pen & ink drawings. One oddity with the earliest book is that the protagonists' names are misspelt; (Stede and Peele) because of copyright infringement concerns.
A selection of stories for fans only, as are all books of their sort. I'll give them a carefully considered 9 out of 10 (if you're a fan) - in short, contact Strictly Literary immediately and buy them before the ebay scammers grab the lot!. A distinct improvement on those awful Norman Douglas books.