I use Canadian-British spellings - any way to change the dictionary in the spell-checker so it’s not always trying to correct my spelling?
Under >> Settings >> General >> Keyboard >> Go nuts!
You can turn off auto-capitalization, Correction, or disable spell checking altogether
You can also try:
Settings > General > International > Language > British English (close to the bottom of the list on mine.)
I don’t know if this is wired up to the spell checking, but it seems a reasonable WAG.
Under “Check Spelling,” all I see is “on” or “off.”
Northern Piper, I’m guessing “no,” since the phone was sold in Canada for use in Canada—if there were a Canadian spelling option, it would be the default.
I tried chrisk’s suggestion, with weird result.
Typed in “colour” and it got red underlining, but no auto correction.
Typed in “labour” and it’s fine.
Typed in “authorise” and it got auto-corrected to “authorize.”
:dubious: 
Your iPhone will eventually learn from you and stop correcting words that you use frequently or that you backspace and “uncorrect” after an autocorrection.
Huh, that’s the opposite of the usual problem! Correct Canadian spelling is “authorize,” so whenever I try to use a British spell-check for Canadian English, I have to change all the “-ize” endings back when they get corrected to the British standard “-ise.”