Learn how to speak english, with a british accent

So for acting purposes and just the pure fun of it, I want to learn how to do plenty of English accents. I can definitely do a British one and plenty of people on the street have bought that I’m British. People in stores have even asked me where I’m from then I’ll say something in American accent every now and then but keep with the idea that I’m British. But I’m not sure how real it sounds to an expert ear. For now, I’ll continue going out with my friend and pulling people’s legs. But please, I’m not one of those people who’s actually going to go around acting like I’m British or something, like for real.