If you are boarding the HC at York there should be "trolley runs" Ex York, Newcastle, Edinburgh and sometimes Perth as well.
With regard to "Regional Catering" unfortunately an unlikely prospect, they struggle to provide the advertised service on occasions without complicating matters further.
Undoubtedly the highlight of your trip will be as the Highland Chieftain pulls into the Grand Metropolis of Falkirk and it's Grahamston Station. Wonder at the architecture of which you will only be subjected to a fleeting glance.