did season 2 of this ever come out?
It says on IMDB that there were supposedly two seasons, with the second one being in 2018, but there are no dates.
I was curious as well, so I gathered up some news. Series 2 has not aired yer, but it was commissioned officially,
https://www.comedy.co.uk/tv/news/2851/back_series_2_channel_4_mitchell_webb/
According to The Sun, it was still being produced a year ago,
https://www.thesun.co.uk/tvandshowbiz/6761709/back-series-two-channel-4-david-mitchell-robert-webb/
Some Redditer claims to have heard of a late 2018 production start date,
https://www.reddit.com/r/MitchellAndWebb/comments/9ag76x/do_we_know_when_season_2_of_back_is_coming_out/
And this trounces all those mere speculations, as Robert Webb announced filming this autumn back in march https://twitter.com/arobertwebb/status/1103192196826755073?s=20
So series 2 will likely come out early 2020, or if editing is really quick, late 2019.