Absolutely regarding the last point. As a typical example, I was quite late arriving for my train at King's Cross and had to join near the back at walk through to my coach at the front of the train. It hadn't even left King's Cross, but the trolley was making its way through coach G so I had to wait to be able to get past it. The other thing is, you can't get a drink when you want one from the trolley. It might appear in an hour or two, or just at the point when you're about to get off.
I do recall one of the TOCs claiming that they did a survey and people said they preferred a trolley to a buffet. However, the answer depends on how you as the question, which can easily be manipulated to steer people towards the desired answer. For example, if you ask "Would you like a trolley serving teas and coffees on the train?" people will, I suspect answer 'yes'. If it was reworded to say "Would you like us to get rid of the buffet and replace it with a trolley?" the answer may be different...