|Thriller-Series 1 and 2||R2UK|
There is one R1 and two R2 editions of Thriller available. The R1edition is a four disc set of the first series only. This set was released by A&E Home Video in September 2006 and has the bonus of a couple of nice extras. The fourth disc contains interviews with Brian Clemens, Shaun O'Riordan and John Cooper and each episode has a brief introduction by Brian Clemens.
The first of the R2 editions is also a four-disc set of series one only. This set was released by Carlton in September 2004 and has no extras. The other R2 edition is a fifteen-disc set of the complete collection of Thriller episodes (all six series). This collection was released in June 2005 and features extras including trailers, the bonus episode Who Killed Lamb?, extended version of Nurse Will Make It Better, US credits, stills gallery and original set designs.
The R2 complete collection seems the obvious winner.