Athena5: On the return flight many got unrequested vegetarian i.e special meals whether they wanted them or not. Why the disparity?
I'm afraid I also don't understand this. Why do you describe that cannelloni dish as a "special meal" just because it had no meat? It seems to me to have been one of two perfectly good alternatives for anyone.
The business of predicting how many pax are going to want each meal type is as unexact now as it was when choices were first introduced into airline catering. Some flights it works, some flights it doesn't. The best ways of ensuring that you get the choice you want are to sit at the forward and aft ends of the cabin, which is greatly assisted by acquiring some frequent flyer status. On BA, buying a W class seat helps enormously too.