Considering the number of the episodes (since Amazon US have 13 episodes).
According to the answer from the official Facebook account (as official as it gets):
12 in UK
13 in USA
Originally, it was planned to air on Saturdays. But due to programming cuts it had to be moved to a Sunday. Which meant the time slots had to be different. So they amalgamated episode 8 & 9 into one. In USA they get the full series.