Just read this about Bourdain No Resevations
Quote:
“
Season 4
As with Season 3, Season 4 was aired in two parts: nine episodes in the winter of 2008, and ten in the summer of 2008. Various sources have referred to the summer episodes as Season 5, but in a post on his blog regarding the September 1, 2008 episode, Bourdain refers to it as the final episode of Season 4.[2] One special episode followed the regular 2008 episodes.
”
So maybe UKTV/Good Food bought it in the two packages and that's why they had the gap.