I can't believe in 2019,people still think everyone in the UK is speaking received pronunciation,especially when the country is made up of England,Wales,Scotland and Northern Ireland - even England has different regions with very different accents. I don't find Scottish accents unusual,especially since the chap from AdoredTV does not actually have that strong an accent.
If you do find it hard to understand,you will have one of heck of time in the UK if you travel around a lot. Also,regarding der8auer his German accent isn't too strong,but I have met some Germans who speak English with a very strong accent.
16y in UK and never understood the argument especially coming from my ex mother in law. I could understand any accent from the start, including the strong Geordie accent two external reps had on my first job in UK.
Yet somehow everyone in the office was amazed how some "immigrant" could understand the them both, while they struggle to understand what they are saying.
Made no difference to me, but possibly is the fact that was already tri-lingual by that time (Greek, English, Italian) and have no issues with learning new languages* or change my accent.
Quickly picked a soft Yorkshire accent, as I was living in Leeds at that time, and while do not sound "native British", I do not sound like Greek either but more Spanish.
*(But always failed to learn German, finding it horrible language that my ears dislike. Contrary to Arabic, Spanish and Mandarin which found easy to learn the last 16y. And especially Mandarin allows me to watch shows made in China in native language and some of them are unsurpassed by the cheap copies made in the West, like the Game of Thrones, 20+ years later).