accent

If you're really into it, and you go to live there for a year or two by the time you were to go back home and visit your family you'd probably have quite an accent. I went to my sister's home town a couple states away from me and came back with a twang of her accent after a week! I love british accents as well. :)

Do you have an ear for languages? If so, you could begin to pick up a British accent in as little as a week. After several months you should be speaking like a native. Ticket to the UK anyone?

It depends on you- it doesn't matter how long you stay in a certain place, but the more you talk to the people(locals) there, then you can also adapt their accent and practice i too. So, maybe two or three months might be enough.