I guess it's a matter of rhetoric, but evidently for marketing reasons the U.K. is now calling what the troops in the BSG trenches called "season 4", which was 23 episodes total including two episodes allocated for RAZOR, "season 4" and "season 5." #4 has 12 episodes, counting 2 for Razor, and I assume season 5 will probably have the last eleven shows and maybe even "The Plan." I do not presume to know the inner workings of whatever deals have been made in this regard, though, so that is what we in the television business euphemistically call "a guess."
The Amazon website listed the boxset as "The Complete BSG", though, and that's not true. Complete until now, yes, complete through what they're calling season 4, absolutely, but "complete" as in every episode of the show? Not so true. However, if you don't have any of the series and would like everything out so far in PAL format, well, here you go!