advice for the weekend away:
I had my hen night recently and had friends staying over who I ate out with and I still mangaged to lose by:
sticking to protein, (nandos is good for eating out, go for the chicken salad, the half chicken affected my ketosis more than the salad did).
avoid alcohol
avoid all carbs, soft drinks (even diet ones) fruit etc...
buy a shaker (from lloyds chemist, holland and barratt, some boots) and take your shakes and shaker with you. stay in ketosis (by avoiding crackers and the like!) and you will find it easier.
eventually you will forget about food (honest) and it wont bother you to be around food, you develop a kind of detatchment.
ultimately - you have to stick with it as much as possible, and keep in ketosis, this isn't a diet you can do by halfs.