When you search for teachers you can change the filter to only see teachers from a certain place. To find your British teacher just select England as the "originally from" option. Then you'll only see teachers who are from England meaning they would likely have a British accent. If you're looking for the BBC accent any of them could probably teach that but if you want a specific location (London, Yorkshire, etc) you'd have to ask them individually or check their profile pages to see the listed city.