Let us know how you get on. The website says different and it was updated recently. Chiltern withdrew the catering!
I was on the 16:15 from Marylebone on Wednesday 12 July, which I believe was after the effective withdrawal of the catering service. At the table was a box containing some bottles of water and some bags of "popcorn", whatever that might be, which I didn't investigate. No leaflet of any sort explaining what it might be, but presumably we were intended to work out that it was included in the fare (I didn't need to pay to upgrade because my ticket was already valid). At Solihull someone got on and removed all the boxes from the tables. I wasn't hungry since I'd had a good lunch in London and didn't have any expectations of any catering service anyway (thanks to this forum), and otherwise it was a nice journey for me at a lot less cost than the normal WCML from Euston, and I wasn't in a hurry to get home.