There are three general types of British accents in England: Northern English, Southern English, and the Midlands accent. One of the most obvious features is whether "bath" is pronounced like the a in "cat" (as it is in the US and in Northern English dialects) or like the a in "father" (as it is in Southern English dialects). The generic British accent, meanwhile, is known as "Received Pronunciation," which is basically a Southern English accent used among the elite that erases regional differences. Here's a video of one woman doing 17 British accents, most of which are shown on the map.
Credits: 25 Maps that Explain English