Just two comments.
Besides the limited period at LHR, you might also run into some overzealous third-party check-in agent at some "foreign" (non French) airports. But that's an exception seldom encountered.
OTC: I was checking in at CDG to EZE in biz a couple of weeks ago. There were a few pax with their suitcases open trying to stuff things in their (allready-overloaded) hand luggage. AF was strictly enforcing the 23kg limit per checked item or PAY. A lady was furious, she was Plat in Biz and was therefore allowed 3 suitcases. She only had one but 32Kg. Doubt that her 3 hand luggages she finally carried satisfied the weight limit.