Avanti offer a light meal, snacks and drinks in "proper" 1st, so it had to fit "lower" than that.
My experience over the last three months is that the limited offering is often even more limited on the day.
So I would reckon about half the trips I have made recently then my first choice of food/snack or soft drink have not been available.
I also would observe that service standards and presentation vary quite a bit - some of the staff are bit switched off. So compounding the lack of availability is the delivery of something you didn't ask for - or non delivery of what you asked for because somebody esle presumably received it. And this is on near empty services.