I can't take it anymore, I don't want to be here?

For as long as I can remember, my grandparents always beat me If I did something wrong. Their deffinition of wrong is "crying to loud" or "not going to sleep", silly little things like that. They only stopped when they realised I could do something about it, when I threatend to call childline if they ever layed another finger on me. Since then, my grandad decided to verbally abuse me. He seems to get some sick thrill out of upsetting me. If I did something "wrong" he would get up in my face and start screaming at me till I cried. If I cried "to loud" he'd scream some more. Now I'm old enough to answer back, oh he hates that. Sometimes he'll grab me and push me around, the other day he even tried to hit me round the face. About half an hour ago I was having a minor argument with my Grandma (Really personal buisness). I was already crying, so my Grandad decided to stare at me and smirk. He wouldn't take his eyes off me and was smirking like Cruella De-vil (101 Dalmations). On top of that, they wont redecorate my room. We've had the same carpet in here for 25 or so years. It's never been hoovered because my Grandad refuses to buy a hoover and the last time It was brushed was 5 months ago. We've had to take the wallpaper off one wall because the wall has a damp problem. There seems to be dust on everything. My books, the tv, the dvd player. I can't possibly write everything here, but I can't deal with the way they talk about me, treat me and I can't tell anyone. What can I do?