HD gets it pretty right for how it was. I have a few more GCEs than him but still only O Levels and I don't think that made much difference to my ability. As for management, I tried it it for a few years and considered myself lucky to get back to full time controlling without losing out. As for how it is now, a degree will help in getting you into the recruitment process ( maybe some of us oldies disagree but that is how things are structured ), it will also provide a plan B if you don't make it through training and it is important to remember that the recruiters still haven't cracked the aptitude testing so the drop out rate is fairly high. IMHO the main predictors for success are aptitude, about which you can do nothing, and motivation. In other words if you can't do the job, and some people simply can't, then all the qualifications on earth won't help but if you have the basic aptitude then sheer determination will see you through. Regarding where to train, I baled out of NATS half way through my career but I do think they provide the best training even now when they have cut things to the bone. As far as industrial relations go, these things tend to be cyclical in my time I saw good and bad periods both with NATs and with other employers.
In short my advice is go for it, it remains a good career if you have the aptitude, I did 42 years and don't regret any of the ATCOing.