To work in a primary or secondary school as a qualified teacher you should have Qualified Teacher Status (QTS).
If you are a graduate, you can complete a one year Post Graduate Certificate in Education (PGCE). There are also part-time and flexible PGCE courses available.
If you are an undergraduate, you can complete a Bachelor's Degree with QTS in either 3 or 4 years or do a non-teaching degree followed by a PGCE.
For information on training to become a teacher, contact the Department for Education (DfE). They can provide information on entry requirements and on local providers.
Teacher training courses
You can find courses at Croydon College, London South Bank University and John Ruskin College.
Croydon College
London South Bank University
L5 Certificate in Education in Further Education and Skills sector
L6 Professional Graduate Certificate in Education (PGCE) in Further Education and Skills sector
L7 Postgraduate Certificate in Education (PGCE) in Further Education and Skills sector