NATS or Serco.........disagree with Jack-Oh, NATS would cost at lot more in the long run, look & at their pay & conditions, for example. Also if they centralised your approach function then the airfield would lose the option of kicking out NATS at a later point, ie. if the on airfield equipment was run down.
Serco would be more cost effective but they have a terrible (abd deserved) reputation with keeping hold of staff, I know I work for them. They insist on a 20% profit on everything and make that by screwing the staff..........apparently that's the fashion everywhere these days
FT