I did a similar trip last week, 2 hours to airport, flight to UK followed by 4 hours in a coach. With all the waiting around
it took almost 12 hours in total.
I ate breakfast normally, coffee at French airport, checked sugar and was relatively high so didn't 'need' a cookie.

(I was a bit worried about security and pump). Arrived in UK and ate lunch at airport. Bought a microwave meal, and fruit salad at airport Marks and Spencer to eat on arrival. No problems,