Having traveled the world quite a bit I can attest to the ubiquity of the word hello… almost everywhere I go it is understood. ‘OK’ has a similar ubiquity, and it is interesting that both words are relatively new additions to the English (universal?) language.
I did once read a Christian complaining about it because it had the word "Hell" in it. A minority opinion of course.
So, not just Scotland but North East Scotland? (I'm in the shire myself, previously Aberdeen)