GhostUK,
Ground Movement Control is one aspect of Aerodrome control. at a quiet airport you might have one ATCO working. S/he is actually doing Ground Movement Planning, and Ground Movement Control, and Air Control.
At Heathrow, we are so busy we have to separate those jobs out, so we have one Ground Movement Planner ATCO, three Ground Movement Control ATCOs, and two Air ATCOs.
Some Approach Controllers work at Swanwick in London Terminal Control, others work at the airports they serve (Birmingham, East Mids, Glasgow etc).
At Heathrow Tower, we earn roughly the same as ATCOs at Swanwick, and all NATS' airports are banded for pay, so that Gatwick earns less than Heathrow, etc etc.