Please, check this Webquest I've just created. You'll have to choose in which city you'd rather live for six months, London or Manchester. Inside you'll find useful information. Lots of videos are included! You'll find the link below the picture. Enjoy.
Each English-speaking country has its own way of pronouncing and modulating words and sentences. Even in the same country you can find big differences between regions (and even in the same city). A working class kid coming from the East End of London speaks with an accent different than a high-class guy from Knightsbridge.
But, probably, the biggest and more popular differences are those between English and American speakers. Watch this video and try to detect the main differences between the boy -American- and the girl -English-. Which accent do you prefer? Both of them are great, don't you think?