Before NATS got the contract, we had a controller at Farnborough who resigned from NATS for a job in Gib, (can't remember if it was SERCo or Airwork) then when NATS got the contract, they re-employed him!
There are people who got chopped during training by NATS ‘cos they were ‘not good enough’ who have ended up back with them at some later date. And I believe not all were happy with that.