You probably have your best picks already and some strong opinions about them as well. Nevertheless, I will brave to offer my personal favourites to you.
First of all, it depends on the English level you would like to start with and how much of a movie buff and a binge-watching creature you are. Something easy for starters could include: The Thin Blue Line or Keeping Up Appearances followed by You Rang M’lord with a dash of Blackadder and a series of good ol’ Monty Python as your level improves.
Not a fan of these old sports? Not a problem! A course made of The Office, The Very British Problems, Little Britain, a splash of The Crown and Victoria together with Peaky Blinders will not only cover the language but it will give you a good cultural background and understanding of this rather eccentric crowd. To get even more insight into the souls and minds of the islanders I dare you to try: Two Doors Down, Years and Years, Hinterland, Shetland or Taboo. All phenomenal stuff.
As you can see, the list is rather long, variated and heavily biased with British English, which is my personal favourite. However, I shall not stop you from more adventurous and bold decisions to go and try other possibilities that are available in the vast English Sea like these: Flight of the Conchords, Grace and Frankie, Westworld, Final Space or… wait for it… The Witcher. I bet you did not expect the last one coming!
The options are limited only by your broadband speed and the offer streaming platforms have at the moment. The most important thing is however to be able to really benefit from it: watch it without subtitles for the first time, turn them on only if they start speaking Glaswegian – let’s be honest, Trainspotting had subtitles for the Londoners, so you are totally excused. Make sure you take notes and return to them regularly. Last but not least: use the language and phrases you have heard.