Reading this thread brought back a lot of memories. PBS ran several of the best.
Now a new series of rewrites has come along and there is a new Miss Marple. The acting and scripts are adequate, but I think it will be impossible to surpass Joan Hickson. All of the Miss Marple- Hickson episodes are available on 5 DVD's in two sets.

I have been getting catalogues from "Video Collectables" but find that Amazon.ca and Amazon.com are cheaper.

Others Available:
Nero Wolfe. Set 1, 3 DVD; Set 2, 5 DVD.
Midsomer Murders. Six sets of DVD
Rumpole of the Bailey. 3 sets
Morse. 6 sets
Philip Marlowe. 3 DVD
Cadfael. 4 sets
Tinker, Tailor.., Smiley's People 6 DVD
Poirot (Suchet). 12 DVD (list price $249.98).
Tommy and Tuppence. 7 DVD (Packaged as A. C's Romantic detectives)
And many others, including the repulsive Cracker. Buy them all (or buy an automobile!).

Missing, unfortunately, is Australian part-Aboriginal detective, Napoleon Bonaparte (a great series of which only a few were shown here. A victim of PC?