Hi. probably the British Accreditation Council at http://www.the-bac.org/
can best answer that question. If you are looking for a career in TEFL/TESOL, remember that the least of the potential employers will be accredited by the BAC, and certainly none outside the UK, and that the number of students in a class can range from 1 to 60!
If you are a student wishing to study in the UK, probably the easiest thing to do would be to email the schools that interest you and ask them directly.