The 'problem' was sorted by a couple of passengers being bumped up to First. To be fair to the airline and the ground staff, they eventually got round to this solution without there being too much 'debate'. And I'm sure that the amenable, good-natured (mainly) Brit holiday-makers would have assisted in the matter had it not been sorted outside the aircraft!
The flight (both ways) was excellent, and helped immensely by a very attentive set of flight attendants and a very informative crew on the flight-deck. And the hol. was good too, thanks.