Okaaaaaaaay, a few very worrying items mentioned in your question hammerman. The Care Standards Commission has an anonymous "whistleblower" line that you can call and report all these shortcomings to.
I worked as a management NVQ assessor for nursing and care homes for three years. The industry comes under an intense amount of scruitiny and I'm shocked but not surprised that this has been allowed to happen.
You talk about "dangerously low " staffing levels; the Commission has something called a "staffing notice" which is a minimum legal requirement of staff ratio to residents, all staff working in this environment legally have to have moving and handling training, and the accident book probably was hidden from staff to prevent the manager from getting a black mark against her name when she was inspected.
You need to contact NCSC as soon as you can and relay these points to them, the home will be then subjected to an unnannounced inspection and hopefully these points will be addressed. Good luck!