I'm more likely to suggest a particular meal and see if it meets with approval

I certainly prefer being asked about whether I eat a specific meal or not. It's easier to judge whether or not a person('s food) will make me ill if they tell me in advance what's being made.

Also, if the guest is bringing the wine, then telling them what you're cooking in advance can help them select an appropriate one :-) (Not that I know too many people who are that serious about wine, but it can happen...)

So, for example, I should forgeo usual practice and clear the menu with you beforehand, rather than just take the list of Becky-food-requirements I have and work it out from that?

Oh, no, not if you don't want to.

Anyway, I think that when you asked me, it was lent and that's a subset of the things I'm eating out-of-lent (the only ones I kept up properly since the end of lent are no chocolate and no caffeine, but they're an addiction thing as well as a tummy thing) and so would likely be moderately low risk to my tummy.