Followup: Just wanted to thank everyone for the good advice!
I enjoyed the evening meal service from Cardiff to Hereford (was prepared to travel onto Shrewsbury if needed) and the pleasant staff had it timed so that I finished desert by Hereford. They were a friendly and convivial bunch.
I ordered the salmon starter, the roast lamb (generous portion) and the chocolate cake with ice cream (that was instead served with clotted cream). Apparently they ran out of ice cream. How do you run out of ice cream leaving the terminal (and my desert was the first to come out of the kitchen)? If catering supplies are replenished in Holyhead, I can't imagine there being much call for ice cream on the breakfast service.
Do the same crew work both the AM and PM services? if so, that must make for a long day! If not, and they cover only the AM or PM, are they assigned other tasks to fill out an 8 hour day?