back on topic, there is a catering service on some trains on the Heart of Wales line but as far as I can tell is hit and miss whther it is on the train as it run independantly from ATW▸ . again, this all stems down to the close relationship with the TOC and HOWLTA who do a fantastic job in improving services on the line.
If anyone would like any more information on the line I will try my best to answer your queries. For a small line there sure is a lot to talk about.
I'm pretty sure the saturday service nearly always has catering - I often get the first service to crewe from ludlow which unexpectedly has catering on it - its the trolley to work the HOW lines