I am looking for a good value single parent holiday for a mother (me) and my son and daughter.?

I have found some web sites which claim to have special deals for single parent holidays, but they cost soooo much. Am I just looking in the wrong places?? I have not taken my children abroad before, and never holidayed with them on my own before either. I am just looking for a week abroad somewhere family orientated, and I can't afford 800 quid odd! If thats how much its going to cost me.. then its camping again in Hastings!!! If anyone has any ideas, maybe single parent clubs who do good deals (although Iv not found one yet) or anything similar really. PS... we are happy to camp abroad however.. we just want to go on an areoplane!!!