It depends what you mean by not up to scratch. They should have basic accommodation that is reasonably clean (if it's not up to their standards they can get some cleaning stuff and clean it, right?), safe and they should be given reasonable provision of food etc.If things aren't up to scratch, do you think they are justified in their complaints?
If they have valid concerns of course they should be free to raise them.
Of course, if they feel said issues aren't being addressed, they could leave for another country that might have higher standards in these areas than us.