There is no typical British accent there are hundreds.

So you wanna learn how to speak in an RP accent. Very few people in the UK actually have that accent so if it's an interest it's worth looking for people who live in what we call the Home Counties to teach you. They're the ones most likely to speak like that. Otherwise focus on general sounds British people make, for example the schwa and a non-rhotic 'r'.

What do you mean?

@John But I think when people say British accent they mean the accent that is being spoken in famous movies, like Harry Potter.

I think means THE one, you know the one that most people don't actually speak. Like the very, VERY WARM welcome that only BBC World News readers offer us.