Given what I've heard lately from within NATS, especially with regard to the quality of management at all non-op levels (and about what happens to management, even quite senior, when they stand up for their staff even just a little...), I'm amazed there are still people repeating the old mantra that NATS is the best ATC company in the UK to work for!
Prospect's ATC section should have been renamed "The Swanwick and London Controllers' Union" about 6 years ago, or possibly the "We're Alright, Stuff the Newbies Union". I was very happy, shortly before leaving NATS, to cancel my direct debit to Prospect.
Frankly, I wouldn't be surprised if Serco, should they buy up the remains of NATS, did a much better job than the Airline Group.