Job security
As for job security, what the other posters mean is that there's no chance of some of the UK airspace becoming operated by another company - it will always be NATS (or another organisation) that controls all of UK airspace, so once you're in, you're sorted.
However, for aerodromes, the control function is contracted - if NATS loses the contract, then you might lose your job. It's not bothering me too much, and I'm on the Aerodrome course with CJayne too, but something to think about.