There's a book called "The Drama Research Guide", published by Kaleidoscope, which covers a huge number of drama programmes (so it wasn't intentionally a comedy!). I found a list of the programmes mentioned, and "Murder at the Wedding" is in there.
Try the Kaleidoscope Publishing website, although I think it's out of print.
http://www.kalpublish.org.uk/books.htm
The following actors appeared (not a complete list): James Hazeldine, Gennie Nevinson, Liza Goddard, Christopher Biggins, Bryan Marshall.