I'm sorry to hear of your daughter's plight jacksgran, you must be so worried. My sister is in a similar situation, married to an immigrant, who only wed her to stay in the UK and he treats her badly, makes her work, whilst he stays at home and encourages her to steal money from my elderly mother.
The only solution is for her to get out of the marriage, but I'm sure you've told her this a million times over. Whilst you can advise her and offer her support, only she can take the steps to leave this abusive relationship. It certailnly isn't good for her children either.