This may seem like a strange recommendation, but the Harry Potter series would provide a great insight into what it's like to be a teenager in modern England. Obviously it's got a lot of mythical stuff in it, but otherwise, and especially with regard to characters, it's very 'realistic'.
I think The Lord of the Flies was a great recommedation, by the way; it would be of great use to a non-native speaker.
Here are a few more to check out;
For modern England:
The Secret Diary of Adrian Mole - Sue Townsend
The Day of the Triffids - John Wyndham
The Wasp Factory - Iain Banks
The Curious Incident of the Dog in the Night-time - Mark Haddon
For old-fashioned England:
The Diary of a Nobody - George & Weedon Grossmith
Dracula - Bram Stoker
Treasure Island - Robert Louis Stevenson
The White Company - Arthur Conan-Doyle
Have fun!
-Nyarlathotep