Boadiceawhat an awful position you are in but we are treated the way we allow ourselves to be treated. Your son and dil have pushed and pushed the boundries because you let them away with it, i know that is harsh but you know its true, I used to allow my son stay in bed all day after he left school, I allowed him to go without a job until the day when he was 25 and I had enough. His life is so different now, he has a place of his own a job and my respect.
Your son and dil are in a mess of their own making and will never learn if you keep bailing them out, they are responsible for housing and feeding THEIR children not you. They steal from you and use you, ask yourself this, if you needed a roof over your head tomorrow or a meal and £50 would they provide it with good grace ? only you know the answer to that.
Do your son and dil respect you ? but more importantly do You respect them.
We only have one life, dont let others call the shots. And yes you are right to be upset.