Little late on the thread, but I did my Work Experience back in 1995 at NATS Gatwick. Spent some time in the office, a couple of days in the tower and also visited other places round the airport (Fire Service, Airfield Ops etc.). Had a fantastic time! The following year I went back for 3 weeks to help them do a runway occupancy survey and pretty much spent the whole 3 weeks sitting in the tower.
Of course it helped that at the time, the general manager of NATS at Gatwick was a good customer of my Dad's (car mechanic).