Apparently it was acceptable to use s or z in words like catalyse or analyze in British English until Microsoft Word came out with a British English spellchecker that picked the s spelling as its standard. Whether this is just myth or fact seems to be a point of controversy.
Most academic and technical writing in the UK still uses the z form, and the OED and Collins dictionaries tend to prefer it, too: https://en.wikipedia.org/wiki/Oxford_spelling
In popular writing, the s forms dominate - I've not heard the MS Word explanation before, but the most popular UK-produced word processors and spellcheckers in the 1980s (eg. Locoscript/Locospell, Protext/Prospell, 1st Word) tended to come from companies in the Cambridge area or which were founded by Cambridge grads, so would naturally have used the s spellings by default.
> Most academic and technical writing in the UK still uses the z form
'z' forms are generally used for writing for an international audience, it hasn't really caught on more generally than that.
I'm British, but when submitting papers for blind review, always use American spelling for obvious reasons. I suppose I could change it after acceptance, but that would just be pretentious.
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.
Both -ise and -ize are UK spelling. One is favoured by Oxford and the other by Cambridge.
No, see (even the new) Fowler's Modern English Usage. British usage is -yse, but right-and-proper Oxford spelling uses -ize, not -ise, for words with a Greek root.