bad at radar,
Yes, and when I signed up many years ago lots of my T&Cs were different to what they are now.
Over the years various deals have been done where these T&Cs were changed. Some changes I liked, some I didn't but they were all (as far as I can remember anyway) done by democratic means ie they were voted on by union members and accepted or rejected.
I didn't like the recent bung and change to the redundancy agreement for example, but the majority accepted it so that's that.
Over the years to come many of the T&Cs you have now will change, some for the better and some probably for the worse. Your first exposure unfortunately seems to have been a change for the worse but that's just the the way it works. Nothing is guaranteed either in life (apart from death) or working for NATS... not even early gos!