If you are not in the mindset of 'oh it's anime it must be kiddy ' then I definitely recommend Fullmetal Alchemist Brotherhood, and Steins Gate. Some of the best titles that have come to the UK Netflix in a long time. Out of all the anime titles, whatever region those two without a doubt recommend. These two titles are addicting, emotional, have cool characters and great storytelling.
Also even though they have no connection to each other, I'd advise to watch Steins Gate first, not because the latter is 'better' but more in the sense, they both have a set of characters you will feel emotionally invested in, but I see Fullmetal as the series that has more characters to be invested and it's the longer series with a bigger storyline and more worldbuilding. If you watch Fullmetal, you could possibly feel underwhelmed going to into Steins Gate.
Steins Gate does start off 'slow' but it's for a reason and builds well to the second half. The details in that series are important from start to finish, so don't casually watch and do other things, otherwise you will be confused and frustrated. Actually do not do the same for Fullmetal, not because it is hard to understand, but you will get a lot more enjoyment.
I know this post is longer than most or probably all, but I needed to be specific.
