Minimum Unit Requirement at Swanwick is 2 sectors on both Tactical & Planner. The Tac is the ATCO that controls the planes while the Planner does all the co-ordinating.
Swanwick sectors are,
Daventry, Lakes, North Sea, Clacton, Berryhead, Bistol, LUS, LMS, Dover & Hurn.
These are then divided into smaller sub-sectors, I think about 28.