Sounds like a wonderful dramatic romp, and has just appeared here:
I’ve only skimmed through the first episode, although I know the Greenwich Phantom reviewed it a while back. I didn’t see much of Blackheath in the parts I watched, just a load of wobbly looking sets (a little bit of Greenwich Park appeared during the first episode). If anyone’s seen it, and enjoyed it please let me know – I’m afraid it looked a little hammy for me!
It’s based upon this book: The Blackheath Poisonings: A Victorian Murder Mystery. If you want to get the full series, you can get hold of the DVD here: Masterpiece Theatre: The Blackheath Poisonings  (REGION 1) (NTSC)