Definite inconsistency with dating here around Sarah Jane. Saying she comes from 1980 can't be right, but everything around that era is pretty messed up.
Actually, it was later on that was messed up. The 60s & 70s UNIT stories were normally implied to be slightly in the future - eg Britain had a manned space programme, there was a BBC3 etc. It wasn't till Mawdryn Undead the dating became inconsistent.
This is one thing I never understand. It's confusing and all over the place, but it doesn't make a huge deal in the grand scheme of things so I don't know why fans obsess over it so much
I don't obsess about it, I just think the original dating assumption makes more sense.