from the NATS website you've "read"
Initial training to become an Air Traffic Controller (ATCO) takes place at our College of Air Traffic Control at Whiteley, Fareham.
Students begin their training on the basic course which last approximately two months. On completion they will then be allocated to either an Area course or Aerodrome/Approach depending on the business requirement at that time.
Area students and Terminal Control students will then continue the college course for at least nine months, Aerodrome students for five months and eight months for Aerodrome/Approach students.
If successful at the college you will then undergo validation training at your unit,