Hope the people who know its not your natural accent won't think you sound affected. Just saying.... If I went to the UK and used a British accent, i think my British friends might think I was making fun of them or trying to be silly.
Absolutely! I'm American(never been out of the country, in fact.) and when I was about 3 I saw a movie and a girl had a British accent and I absolutely loved it and I somehow managed to teach myself to speak that way and now I can speak with a British accent whenever I please.