No, but from what I've been told by those who work in FMU is that in working out who gets an upgrade, the system will upgrade those without special meals unless and until they run out of options. So if an OpUp is more important than catering (or you have your own supplies anyway) then I personally wouldn't put a special meal down. That isn't the same as pre-selecting a regular meal for departures from London via MMB, that has no impact. As far as this particular flight is concerned, it's way too soon to be sure how it is looking, it would be better to look at the numbers and seat plan at say 36 hours to departure and making a decision then.