@Jacob oh that's a shame about the book store.

I always hear people from England saying 'Why would you wanna live here? it's so gloomy and rains all the time' but that's actually a big reason why I wanna go to England.

And, this is so random, it's such a minor detail

, but.. the grass! It must be so green

among other reasons
I didn't know that the HP book contents didn't shift much

I imagine it was a bit easier to show the characters maturing in the movies, considering the actors WERE actually growing up while filming. I just know that there is a very definite and obvious maturity throughout the movies. The first ones sit more as standalone movies than the later ones. I feel like the movies move from being a bunch of kids on an adventure/s (you can watch the philosopher's stone, for example, without needing to watch the next movie to understand the story) to relying a lot more heavily on the storyline and complexity that has been built up throughout the series (eg in the later movies I feel like I need to watch the next movie to get a full sense of the story and have questions answered or storylines feeling complete).
And I think that because the first movies feel more like standalones it kind of further emphasises the intended audience's age maturing. Like you don't expect a child to be able to understand or have the attention span to follow along with a complex storyline as much as you would an adult.