[gbil]

I learned British English starting in the 80s and using s whereas z was used in American English, together with tre instead of ter (eg. theatre), was a big difference. And I can tell you that MS Word back then was just not there so this sounds like an urban legend but let the British people in HN chime in.

[nephihaha]

Both -ise and -ize are UK spelling. One is favoured by Oxford and the other by Cambridge.