>have we established there is indeed a "once-only 'ou' " rule

Sounds plausible. [knowing wink emoticon]

On the subject of colonies. It is allowable, amongst consenting adults, to refer to the parts of Britian furthermost from the capital as the "provinces". I think, like colonies, in the right company, it isn't an insult, just an "in joke" amongst us provincial types. The main problem is finding the right company in which to use the term, otherwise the results can be painful! I note that "Antipodean" gets similar results!