RPPArgy - glad you are not too offended by the pep talk! Also south beach is not atkins, and anyway whatever diet you are on you'd have gained it afterwards if you ate a lot again.
In terms of cheats - for me its a cheat meal of an extra around 500 cals BUT I never eat my exercise calories so think that this covers it.
FWIW I went to America over Easter on all expenses paid holiday, all inclusive, 3 amazing meals a day laid on PLUS all day tea room containing cakes, biscuits, sweets, cakes, ice cream, chocolate, drinks & sushi(!). Plus all day burgers, chips, chicken, kebabs laid on too. Plus as much fizzy drink, wine, juice as I wanted.
I decided that although I wanted to enjoy the food I would not risk undoing the good work.
Breakfast I had massive omelette and fruit. I tasted the waffles (1/4 waffle) one day, 1 pancake another, 1 freshly baked cake another etc.
Lunch I had vegetables and grilled fish only. Dessert a couple of times.
Dinner I had the starter and main course (although left carbs) (it was plated)and the dessert some days. I had one glass of wine.
No juice at all whole holiday.
Went to burger tent once and had a few of DD's chips.
Was restrainted in tea room..... 3-4 little dark chocolates.
Did loads of exercise. Did not eat if full.
Came back having only put on 2lbs which I lost in first week back.