The most recent rankings list, from the EL Gazette (an independent publication, covering English as a Foreign Language course providers) I can find is a couple of years old but it should still provide a useful starting point: https://www.elgazette.com/wp-content/uploads/2019/08/EL-Gazette-UK-Language-Centre-Rankings-2019.pdf
Sorry, we can't find any related questions. Try using the search bar at the top of the page to search for some keywords, or choose a topic and submit your own question.