I have just discovered this rather talented teenager on Youtube. He certainly has a gift with sounds and accents. I would recommend him to anyone inspite of the bad language you might have to listen to, f.... and c..... words! It seems to be part of his stereotyped presentation of the characters. He does apologise at the end for this himself though.
Enjoy it and learn at the same time:
http://www.huffingtonpost.com/2010/10/01/24-english-accents_n_747400.html
Now try out a few more accents being introduced to Amy:
http://www.youtube.com/watch?v=3UgpfSp2t6k
Then learn a little bit of theory:
http://www.21accents.com/21_Accents/About_Accents.html