According to play.com and amazon the release date is now 20th October, not the 8th as quoted originally. However Network are showing it to be 8th, so I guess we will find out on Wednesday.
Both play.com, network and amazon now have the "Complete series" artwork up for those of you who havent yet seen it - however it is the same artwork as series 1. Both play.com and amazon also show the release date for the complete series as the same day as series 3; again Network are showing the 8th.
So it looks like they have pushed the release date back.