sauvignon do you have any insight into why you ate all of that? Did you have one item then think fuck it I might as well have all the rest? Were you somewhere out of the house with no other option? Did you notice whether eating some carbs set up a craving for more, or made your blood sugar unstable leaving you hungry and tired? You possibly want to draw a veil over it all, but thinking about what caused it, and how you were making decisions along the way can be really helpful in preventing your from a repeat of the same.
If you're tempted like that then I found it really helpful to plan my shopping and meals. Even if there were crisps for other family there were only 2 packets, so none for me, plus I plan an alternative snack that is lchf (and extra delicious) - pate on M&S pork scratching whirls, celery and blue cheese, microwave exploded babybel- whatever works for you.
I freeze sliced bread and get out just enough for dh (so there's not a loaf sitting tempting me). I buy cake that I don't like (but which dh loves) and I always have an alternative ready.
For the next 2 days you need to be well prepared. If you're somewhere urban then breakfast should be easy, any greasy spoon will do eggs, bacon, mushroom... Or look up places that are local and plan what you will ask for. Others recommend Leon for truffle-mushroom-poached-egg-pot, or smoked-salmon-and avocado-egg-pot.
At lunch time, scout out the local shops. Is there an M&S nearby? Plan what you will have. In the event that they get in sandwiches, fruit, cake, have an excuse ready. Say you have to go for a walk to make a phone call, take bootcamp friendly snacks with you, a boiled egg, something from M&S, a few nuts. If you can't tell them that you're not eating carbs tell them you have a nut allergy and can't eat 'unlabelled' bread (just make sure you don't then eat your nuts).
If you don't go prepared then it is too easy to slip into all the wrong food types, particularly if you are stressed, tired, hungry. If all else fails eat a high fat breakfast (butter coffee before you leave home will help) and use the rest of the day as an opportunity for some time-restricted eating. But, if you're doing this plan out what you will eat as soon as you leave the client, so you have something to look forward to immediately and avoid grabbing a bag of crisps at the station. M&S rollitos, M&S prawn snack pot with cocktail sauce...