I must admit, even on the same train the service can be variable.
I was on the 0930 London - Edinburgh today. Out of London better than expected, full breakfast, I was only expecting the bacon butty. Maybe they still had food from the inward journey.
however from Newcastle the trolley came through, one run of coffee, one run of drinks and the food then attempted to have the train cleared up by Alnmouth. I would not be impressed if I had joined at Newcastle (which is still over 1 hour away). Poor Alnmouth at 65 minutes gets nothing, not even a tea / coffee.
The other thing that was odd, they were asking passengers from York if they had had breakfast. Does that matter if you had split your ticket and got 2x APs which should get 2x meals (and would still cost a lot less than the Open first which only gets you one)