The United Kingdom and Ireland take up the British Isles - those landmasses just across the Channel from France where everyone speaks a very slightly different version of English to the person next to them. How you talk is an excellent way to figure out which part of those isles you come from, and even more things about you, such as what sort of school you went to and what job you're lucky to have.
These traditional distinctions are happily growing weaker with time, but there are still some strong correlations that mean a person's accent does give you a certain amount of information about them that is probably correct.
Some British accents are universally known and understood, such as Received Pronunciation, AKA the Queen's English - which is the one that you've heard James Bond and the Lannisters use - and standard Scottish English - which you'll recognize from actors such as Ewan McGregor and David Tennant.
Others are more obscure and harder for foreigners to grasp; for example when the movie "The Full Monty" originally came out, some American audiences needed captions to understand what the Sheffield-based characters were saying! That means, of course, that there are lots of ways we might figure out what accent you have. Answer a few questions and let's see how we do!