Wording for pestering a guest who says they're coming but hasn't Rspv'd?

Would you not take them saying they are coming as a RSVP, or is their specific information in the RSVP that you need from them.... perhaps a call in this situation would better if they are close friends, that way you can explain the situation and stress the importance for a formal reply. Some people are naturally a bit rubbish at sending back RSVP's.
... side note, a B list is a fantastic idea, that I will now be adopting!!!

Agree with what Sophie says. I've just been calling friends direct or messaging them and asking them to confirm whether they will attend and also to choose meal options. If they can't do it on website I can update planner myself if they let me know either way.

My deadline was today. Most of my people i asked have confirmed. Quite a few of his have not so hes getting a list today to start msging tmw for me if needed.
We dont tie the knot til aug but the sooner we know numbers the better.

Personally I would take them saying they are coming as them RSVPing?? If someone told me they are coming then that's confirmation for me, and if when people are RSVPing to our wedding they just send us a text then we will update the website ourselves. How have you asked them to RSVP?

In terms of food I would tell them you do need their menu options today/tomorrow the latest as it needs to be in x

I would just take them saying that they are coming as their RSVP. If you need menu details, then I would give them a ring and ask - it sounds like they are extremely busy and/or chronically forgetful, so a direct conversation is probably the easiest way forward!