I really enjoyed this movie, it's a light drama about a complex subject and era and a kid living a difficult time in it.
It's true that it feels a bit naive and unrealistic in many ways, but the good acting, likeable characters, bit of humour and the music (I'm not even a fan of punk music or The Clash, but it was a plus for me) made me forgive the lack of realism and enjoy a light-hearted adventure.
Also, as I've been living in London for the last 8 years, I really enjoy watching movies portraying the city as it was before I got here, so this is an interesting aspect of the movie for me.
Great movie, not as serious as some may wanted it to be, but very enjoyable.