I know this was written years ago but just some points you pointed out as negatives personally I find vital to character and plot development.
A lot of teenagers (not all) do see the world in stereotypes; its how they try and make sense of the world and where they fit in. So Jem (the narrator) thinks herself and those around her fitting into this "going nowhere" stereotype and accepted that categorization at the start of the story. However, later on in the story as she starts to encounter more of the world through the people she meets and her physical environment, this starts to destroy many her preconceptions of people preset at the beginning of the book.
Also the the reference of the London Eye makes the story accessible to a wide range of readers as almost everyone has seen an image of the London eye, which is in the background of many many films (and I think it may be in the credits sequence for bbc news ?) unlike parliament or Buckingham palace the area around it is accessible to the public and not got the authoritarian connotations.
I hope someone finds this helpful.