[Domestic] What to do?

Long time reader, first time poster (technically a lie since I used to post under a different username a good while ago).

Just had a chat with my mum. Apparently, there's been some problems at home. I knew a little about it but not as much as I do now.

My father and mother married about 28 years ago. Because we're Indian, it was an arranged marriage. All was well until about 7-8 years into it when my father started drinking. Mother was okay with it. For a few years, there were the odd fights and arguments - always when my father had been drinking. I was aware of them as a kid but didn't know much about it and my mother wasn't forthcoming.

For the past five years, this has escalated where my mother has suffered verbal and emotional abuse, and occasionally physical abuse. I was aware things were getting a little rocky but my mother never let on about what had been happening. I had since moved away to uni.

A few nights ago, my mother was in the bedroom, quietly reading (she tends to stay away from my father after 9pm when he's likely to be drinking). He lay down a belt in front of her and demanded obedience. She didn't say anything. At that point, he ran off downstairs and my mother called my sister and they locked themselves in. They called my grandparents who arrived and demanded to know what was going on. My father denied any threatening behaviour.

I dread to think what could have happened.

Something has to be done.

I've been working for two years over 200 miles away and now managed to get a job back in my hometown. The plan was for me stay with my parents and save enough money to buy a house so I could afford to move and take my mother with me. Having heard what has happened, I don't know whether I should move back and try to settle/stop things or whether that would make things worse.

Is there anything else I can do? Going to family for help isn't likely to generate a positive response and I do not wish for my grandparents to come under duress from my father. My sister and mother do not have enough cash to make moving out a realistic possibility.

I don't have enough to buy a house (barely £2-3k in savings as I've been making enough just to survive) so I'm gonna have to rent. This might work but the problem is my father knows where my sister and mother work and I am concerned about him doing something whilst they are going to/from work. Obviously with the economy the way it is, neither is working much (3x/wk max) and neither would be able to find work elsewhere, leaving me as the lone supporter.

I've been looking at womens' refuges and such where my mother and sister might escape to but I don't know if there's anything else or anywhere else to turn to. I feel helpless sitting here.

Your advice is greatly appreciated.