I would suggest that there is not statutory requirement to undertake a risk assessment however it would be wise for you to undertake one. If you are responsible for the cleaners welfare then there are matters for you to consider prior to sending them to properties. Undertaking a risk assessment will demonstrate you considered matters such as high risk tenants, hazardous substances, sharps etc and other hazards they may be likely to encounter in the course of their work.

It might be more helpful if I elaborate! If YOU are 'employing' someone to come and clean YOUR house, then I would suggest that there is no statutory requirement to carry out an assessment, and for the most part I wouldn't suggest that you need to do anything formal either (unless your house has some unusual or 'extraordinary' risks) If on the other hand you are talking about cleaners who are employed by an employer to go and clean another persons house, then the usual rules will apply. Whether a site specific assessment is required, as opposed to something more generic is another discussion.