And -ize is perfectly acceptable to many British English spell checkers. Unfortunately it seems impossible to find one that will reject -ise spellings when the -ize one is the more etymologically 'correct'.

For instance, I am using Firefox with a British English checker and it, correctly, allows "advertise" but not "advertize"; however, it also allows both "mythologize" and "mythologise" when only the first would be accepted in the Oxford tradition.

I'll be sticking with the advice in Fowler's Modern English Usage, Second Edition.