Hi - PPRUNE always astonishes me! What a great and informed set of answers, thanks everyone.
It was a handling agent at ZRH. Very friendly and was making a good effort at least of trying to help, but both we spoke to used exactly the phrase mentioned, i.e. "our hands are tied". They had very limited ability to help us.
Yes, PAXboy, agree that this kind of experience is ultimately self-defeating. For those of us who travel a good deal, the stories about particular airline experiences do the rounds pretty quick and while most people have no idea what plane they're flying on, they certainly DO remember who the airline was (even if it's a code-share and actually operated by someone else). What I mean by that is that the strong brand in the airline world can count against them in these sorts of situations.
Airline tickets these days represent a fair amount of expenditure for certain businesses and individuals and one experience like this can make you quickly put an airline on your personal black-list (mine currently includes EJ, RYR, AF).
Shame, because largely BA are a far more pleasurable company to fly with than any of their competitors. However, the CS have never been too brilliant with dealing with the unusual (delays, LHR limitations, seating issues...).