Disabling Spellcheck (globally) turned out to be a piece of cake....

Actually I feel a little let down:  I was prepared to fight to preserve those soft melting bastard Latinisms and half-conscious Briticisms--but all I had to do was uncheck a little box that I didn't know was checked (in System Preferences/keyboard), et Voilà!  all the colours, honours, favours I could wish.  Maybe even more.