Hi @Anonymous User
I don't follow this TV show, but according to the Sky TV Guide Planner S1 Episode 6 will be aired New & Exclusive on the 20th of October 2020 (see screen shot below).
Therefore this would suggest to me that this TV show is on Catch up and not boxsets (might be wrong).
Don't let episode 7 confuse you, where it is a highlights episode and according to IMDb website the last episode in the series for season 1 is episode 6 titled "Last Day - The Dark".
Plus the description in the episode 6 screen shot below also mentions " dramatic conclusion" which suggests to me the final episode in the season.