The article also goes on to outline how "It is estimated that around two thirds of these migrants work over 15 hours a day and earn under £200 a month." Understandably, many migrants put up with bad conditions because of the threat of deportation, i.e. to be legal they need a working domestic visa, naming their employer and their place of work. The employer also has to sign a declaration every year in order for the visa to be renewed.
In effect, the servant's right to stay in this country depends on their boss, i.e. a main factor in this exploitative relationship is the mutual awareness that whilst demand for domestic help continues to rise, the number of foreign national arriving to fill the jobs is rising much faster.
The question is how do people who are not protected much by law protect themselves? Put another way, how can those who exploit be held to account? It's not an easy question to answer because of significant power imbalance between employer and employee. However, raising widespread awareness of such practices is certainly a good starting point. A next step should surely involve some sort of organized activity along the lines of a trade unionism as regulating a largely underground activity is likely to fail.