I would agree with paperclip810 that having a degree to fall back on is a good thing, and in any case a degree can be its own reward.
I must take issue with HD though, with due deference to his (I believe) being a retired ATCO. It may once have been true that NATS was "undoubtedly the best employer" but these days, at least at my old unit, morale is in the toilet. Some people don't entirely trust the company to fund the pension scheme for those lucky enough to actually be in it, and those joining now have nothing close to the retirement benefits accorded HD and others of his era. The banding exercise of a few years ago was a classic case of management sewing division between different groups of staff, aided and abetted by a union which keeps its powder dryer than might be thought possible in a humid climate.
For those without the money to fund their training privately, NATS is the best way into ATC in the UK, and despite what management may think it's fair to say that 5 years post-training is a perfectly reasonable return of service for those who seek greener pastures. The RAF and RN are probably good for the lifestyle, though not what they once were, and with them the job involves more variety. What they don't offer is the chance to walk straight into a civilian ATCO job without further training.